Apparatus and methods for solution processing

ABSTRACT

Equipment, systems, processes and techniques for conducting processing of solutions are described. The techniques can be applied to provide diluted solution (i.e. purified solvent), concentrate solution or each. A variety of specific equipment, example systems and processes are depicted and described.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. Ser. No.16/277,139, filed Feb. 15, 2019. U.S. Ser. No. 16/277,139 is acontinuation of U.S. Ser. No. 15/693,572, filed Sep. 1, 2017, whichissued as U.S. Pat. No. 10,518,218. U.S. Ser. No. 15/693,572 is acontinuation of Ser. No. 14/492,571, filed Sep. 22, 2014, which issuedas U.S. Pat. No. 9,751,045. U.S. Ser. No. 14/492,571 is a continuationof U.S. Ser. No. 13/544,294, filed Jul. 9, 2012, which issued as U.S.Pat. No. 8,840,792. U.S. Ser. No. 13/544,294 is a continuation of U.S.Ser. No. 12/455,998, filed Jun. 9, 2009, which has issued as U.S. Pat.No. 8,216,473. The present application also includes the disclosure of,with edits, U.S. provisional application 61/131,947, filed Jun. 13,2008. A claim of priority is made to each of U.S. Ser. Nos. 16/277,139;15/693,572; 14/492, 571; 13/544,294; 12/455,998 and 61/131,947 to theextent appropriate. Also, the complete disclosures of U.S. Ser. Nos.16/277,139; 15/693,572; 14/492,571; 13/544,294; 12/455,998; and,61/131,947 are incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to methods and equipment for solutionprocessing. The methods and equipment are applicable to provide purifiedsolvent (i.e. dilute solution) and/or to provide concentrated (solute)compositions. In certain examples, cascading reverse osmosis processesand systems are described. Some potential examples of use involve:brine, desiccant, or deicing fluid re-concentration; salt water,brackish water, ground water or sea water demineralization and/ordesalinization; juice concentration; sugar solution concentration;pharmaceutical purification or concentration; liquid waste or wastewater treatment; and, recovery of other selected (valuable) materialsfrom solution. A unique reverse osmosis unit or module, configured forboth high pressure side and low pressure side inlet feed and outlet flowis described.

BACKGROUND

The present disclosure relates to solution processing. The solution canbe from a variety of sources and processing generally concerns providingone or the other, or both, of: (1) a dilute solution (or relativelypurified solvent) stream; and, (2) a relatively concentrated solutestream (concentrate). The techniques described herein relate to uniqueand advantageous applications of reverse osmosis technology.

SUMMARY

Herein, a unique reverse osmosis unit is described. The reverse osmosisunit includes: a reverse osmosis membrane arrangement; a high pressureside feed inlet; a low pressure side feed inlet; a high pressure sideoutlet; and, a low pressure side outlet. The unit can be incorporated ina reverse osmosis system, according to the present disclosure.

Also, processes, techniques and equipment are described for conductingreverse osmosis processing of a solution. An example equipmentarrangement, used in various applications of the techniques describedherein, comprises a reverse osmosis unit or module, having both a highpressure side inlet and a low pressure side inlet, as well as a highpressure side (concentrate) outlet and a low pressure side (dilutesolution) outlet. Such equipment can be applied in a variety of systemsand arrangements, to achieve desirable reverse osmosis operation.

Some of the example techniques described herein include providing areverse osmosis system having at least:

(a) a first, final, solvent or dilute solution outlet-generating reverseosmosis unit; and,

(b) a first, final, concentrate outlet-generating reverse osmosis unit;and may also contain,

(c) an intermediate reverse osmosis membrane unit system comprising atleast one reverse osmosis unit.

Typically, at least one reverse osmosis unit in the intermediate reverseosmosis membrane unit system comprises a reverse osmosis unit or modulehaving a high pressure side inlet and a low pressure side inlet, as wellas a high pressure side (concentrate) outlet and a low pressure side(dilute) outlet.

Herein the term “original solution” is generally meant to refer to thesolution directed, initially, into the system for processing. Theoriginal solution may comprise any of a wide variety of solutionsdesignated for processing. Although not limited to these examples,example systems could include: brine, dessicant, or de-icing fluidreconcentration; saltwater, brackish water, groundwater or seawaterdesalinization; juice concentration; sugar solution concentration;pharmaceutical purification or concentration; and, liquid waste or wastewater treatment.

A variety of example systems and applications are described, each ingeneral accord with the above descriptions.

In some examples, the processing is conducted such that at least:

(a) concentrated solution (concentrate) from the first, final, dilutesolution or solvent outlet-generating reverse osmosis unit is directedinto the intermediate reverse osmosis membrane unit system, andtherethrough to the first, final, concentrate outlet-generating reverseosmosis unit;

(b) dilute solution from the intermediate reverse osmosis membrane unitsystem is directed into the first, final, dilute solution or solventoutlet-generating reverse osmosis unit as at least part of a highpressure side inlet feed stream thereto; and,

(c) concentrated solution (concentrate) from the intermediate reverseosmosis membrane unit system is directed into a first, final,concentrate outlet-generating reverse osmosis unit. Also typically:

(d) dilute solution from the first, final, concentrate outlet-generatingreverse osmosis unit is directed into the intermediate reverse osmosismembrane unit system, and therethrough to the first final dilutesolution outlet-generating reverse osmosis unit.

Typically, the processes are conducted such that each reverse osmosisunit in the intermediate reverse osmosis membrane system is conductedwith both a high pressure side inlet feed and a low pressure side inletfeed. Further, the high pressure side inlet feed to each unit, in theintermediate reverse osmosis membrane unit system, typically does notdiffer from the low pressure side inlet feed to the same unit by morethan 20% in solute concentration, usually no more than 15% in soluteconcentration; and, often no more than 10% in solute concentration.

Indeed in some processing systems according to the techniques describedherein, for at least one selected reverse osmosis unit, of theintermediate reverse osmosis unit membrane system, the inlet feed to thehigh pressure inlet side and the inlet feed to the low pressure inletside, are the same in solute concentration (but differ in pressure andperhaps flow rate). Also, in at least one system and process describedherein, each reverse osmosis unit of the intermediate reverse osmosismembrane unit system, has a high pressure inlet feed and low pressureinlet feed which, for that selected unit, is the same in soluteconcentration. By this, it is not meant to be characterized that thefeed for each reverse osmosis unit of the intermediate reverse osmosismembrane unit system is the same as every other reverse osmosis unit ofthe intermediate reverse osmosis membrane unit system, with respect tosolute concentration or flow rate; rather, it is meant that for eachchosen unit, for that chosen unit, the high pressure side inlet feed andlow pressure side inlet feed is the same in solute concentration. Thiswill be apparent from a review of the example processes and systemscharacterized in the drawings.

A variety of specific examples, systems and techniques are described. Itis noted that a reverse osmosis process, and corresponding equipmentsystem, can be practiced without all of the specific features andtechniques characterized herein, while still obtaining some benefitaccording to techniques of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a typical, prior art, liquid/soluteprocessing system, using a reverse osmosis unit.

FIG. 2 is a schematic view of a typical prior art liquid/soluteprocessing system, using two reverse osmosis units.

FIG. 2A is a schematic depiction of an example reverse osmosis unitprovided according to the present disclosure with both a high pressureside inlet flow and low pressure side inlet flow, as well as highpressure side (concentrate) outlet flow and low pressure side (dilutesolution) outlet flow; the unit of FIG. 2A being depicted in a countercurrent flow configuration.

FIG. 2B is a schematic depiction of a second example reverse osmosisunit provided according to the present disclosure with both a highpressure side inlet flow and a low pressure side inlet flow; the systembeing analogous to FIG. 2A, but depicting an alternate pump system.

FIG. 2C is a schematic depiction of a third system analogous to FIG. 2A,but configured with a membrane sweeping pump therein, and an alternativepumping arrangement for original solution to be processed.

FIG. 2D is a schematic depiction of a fourth reverse osmosis unit systemincluding two reverse osmosis units therein.

FIG. 2E is a fifth schematic depiction of a reverse osmosis unit system,having two reverse osmosis units therein.

FIG. 2F is a schematic depiction of a sixth reverse osmosis unit systemhaving three reverse osmosis unit systems therein.

FIG. 3 is a schematic depiction of a seventh example system configuredfor operating a reverse osmosis process according to the presentdisclosure.

FIG. 4 is a schematic depiction of an eighth example system for reverseosmosis process conduction according to the present disclosure.

FIG. 5 is schematic depiction of a process for conducting reverseosmosis processing using two systems in parallel, each in general accordwith FIG. 3.

FIG. 6 is a further example system for conducting a reverse osmosisprocess in accord with the present disclosure.

FIG. 7 is a schematic depiction of a still further example system forconducting a reverse osmosis process in accord with the presentdisclosure.

FIG. 8 is a schematic depiction of yet another example system forconducting a reverse osmosis process in accord with the presentdisclosure; the system of FIG. 8 being analogous to FIG. 7 except withregards to original solution entering the first, final solvent outletmembrane unit.

FIG. 9 is a schematic depiction of another example system for conductinga reverse osmosis process in accord with the present disclosure.

FIG. 9A is an example system analogous to FIG. 9, except modified forisolating certain solute movement.

FIG. 10 is a schematic depiction of another example system forconducting a cascading reverse osmosis process in accord with presentdisclosure.

FIG. 11 is a schematic depiction of a further example system forconducting a reverse osmosis process in accord with the presentdisclosure.

FIG. 12 is a schematic depiction of a further example system forconducting a reverse osmosis process in accord with the presentdisclosure.

FIG. 13 is a schematic depiction of a further example system forconducting a reverse osmosis process in accord with the presentdisclosure.

DETAILED DESCRIPTION I. Reverse Osmosis, Generally A. General Principles

An osmotic membrane can be any semi-permeable barrier which allowssmaller molecules, such as solvent molecules, to pass through whileblocking the passage of relatively larger molecules or ions, such asthose of a solute dissolved in the solvent. Osmotic membranes are foundin nature. Man-made osmotic membranes are also in use. A common,classic, example for human applications, concerns a liquid/solutemixture (solution) of salt, minerals and water. In nature, osmoticpressure is partially responsible for the transport of water, relativeto sugars, and other nutrients in plants.

The term “solution” as used herein, and variants thereof, is simplymeant to refer to a solvent/solute mixture; and, more is not meantunless otherwise specified. The term “original solution” is often usedherein, to refer to an initial feed mixture to a reverse osmosis processand system for processing, in accord with the present disclosure.

In general terms, osmosis is a physical phenomenon considered to be onethe colligative properties, concerning the behavior of solutions.Osmosis is a process whereby a solvent will naturally pass through anosmotic (semi-permeable) membrane into a solution of a relatively higherconcentration of solute, thereby diluting the higher concentrationsolute in an attempt to reach concentration equilibrium on both sides ofthe osmotic membrane. The force per unit area which drives this processis described as the osmotic pressure. Once concentration equilibrium isachieved, net transport stops and the osmotic pressure differentialacross the osmotic membrane is zero. Osmotic pressure is generallyproportional to a difference in solute concentration between the liquidson either side of the osmotic membrane; concentration typically beingexpressed in terms of the molarity of the solution.

Reverse osmosis is a process of applying pressure to an osmotic membraneside, typically containing a higher concentration of solute, whichserves to drive the osmotic process in reverse, i.e. drives solventthrough the osmotic membrane from the higher pressure (typically highersolute concentration) side. An incoming solution stream to the osmoticmembrane is referred to as the “feed” stream; and, an outgoing fresh,purified, or relatively low concentration stream which has passedthrough the membrane is commonly referred to as the “permeate.” Anoutlet stream which has an increased concentration of solute, from thehigh pressure upstream side of the membrane unit, is commonly referredto as the “concentrate” stream. An outlet stream which has a decreasedconcentration of solute, from the low pressure upstream side of themembrane unit (for example as a result of mixing the permeate which haspassed through the membrane with other solution), is referred to hereinas a “dilute” stream. The term “dilute” stream, and variants thereof, isalso sometimes used to refer to low pressure side outlet flow that onlycomprises permeate.

Reverse osmosis has been used in a variety of applications for purifyingsolvent, for example to purify water. Nearly pure solvent (in many caseswater) can be derived by forcing the solvent molecules through aselectively permeable osmotic membrane. The pressure required to achievesuch a separation, and therefore purification, must be greater than thenatural osmotic pressure tending to drive the process in the oppositedirection. Because osmotic pressure is a function of the difference inthe solute concentration between the liquids on the each side of theosmotic membrane, increasingly higher pressures are required to obtainseparation (and thus solvent purification) from increasingly highersolute concentrations.

Typically, use of osmosis is inherently limited by the pressure requiredto overcome the resulting natural osmotic pressure as soluteconcentrations elevate. This is a major source of productloss/inefficiency, and limits the useful range of typical reverseosmosis configurations. For example, normal sea water has a typical saltconcentration of about 3.5%. The osmotic pressure of sea water of thisconcentration is approximately 25.5 atmospheres. As fresh water isextracted from the sea water stream, the salinity will rise in theconcentrate, since the salt stays behind and the fresh water is removed.Achieving a 40% water recovery from salt water would require an increasethe salt concentration in the concentrate (i.e. on the high pressure orupstream side of the membrane) to just under 6%. The pressure requiredto achieve an effective recovery ratio of fresh water has to be higherthan the maximum salt concentration of the discharge end of the process,so that the flow can progress from the sea water side to the fresh waterside of the osmotic membrane. The pressure required to drive the processmust be higher than the osmotic pressure at the discharge end of theprocess. Assuming a 40% recovery rate, which implies an approximate 6%salt concentration discharge, the required pressure to be applied mustbe greater than approximately 45 atmospheres, or approximately 660pounds per square inch (psi). That is, a minimum of 45 atmospheres ofpressure must be applied continuously, to hold the process steady. Inpractice even more pressure than this theoretical minimum is typicallyrequired to overcome the pressure drop due to flow through the membraneand other various components.

A typical, commercially available, osmotic membrane is designed towithstand a continuous reverse osmosis driving pressure of up toapproximately 690 psi. Such membranes, for example, are available fromGE Water and Process Technologies, Watertown office, Watertown, Mass.02472. An example of such a reverse osmosis unit is a spiral-woundreverse osmosis membrane consisting of tightly packed filter materialsandwiched between mesh spacers and wrapped in a small diameter tube.

From the above, it should be apparent that an ever increasing drivingpressure is required to increase the total extraction or concentration,for concentrates above a relatively small solute (in the example, salt)percentage.

To achieve separation of solution concentrations higher than can beachieved with typical reverse osmosis systems, past practice has been touse techniques such as: distillation; mechanical vapor recompression;thermal vapor recompression; and/or single or multi-stage evaporators.These are typically all relatively energy intensive by comparison to areverse osmosis process. However, due to operational pressurelimitations of many available osmotic membranes, these methods oftenpresent themselves as the most practical, despite the larger energyconsumption. Another common disadvantage to these non-osmosis techniquesis the thermal destruction or stripping out of various aromatic orflavor compounds, when the technique is being used to process materialsrelating to consumables, for example tomato juice, coffee, or variousfruit juices.

B. Typical Osmonic Membrane Configurations and Use

Numerous patents have been issued relating to osmotic membraneconstruction and use. Example membranes are described in the followingpatents: U.S. Pat. Nos. 4,992,485; 4,980,063; 4,957,817; 4,941,972;4,927,540; 4,909,943; 4,894,165; 4,859,384; 4,859,338; 4,839,203;4,828,700; 4,824,574; 4,812,238; 4,806,244; 4,797,187; 4,769,148;4,765,897; 4,704,324; 4,652,373; 4,358,377; 3,630,378; 3,475,331; and3,472,766. Membranes described in these references, incorporated hereinby reference, can be utilized processes and equipment according to thepresent disclosure.

Commercially available membrane units can be used in the techniquesdescribed herein, if modified as described below. Examples include theGE Water and Process Technologies Unit characterized above.

Attention is now directed to FIG. 1, in which a typical reverse osmosisunit, configured for a typical, non-cascading process, is shown,schematically. Referring to FIG. 1, reference numeral 1 indicates thereverse osmosis unit. In accord with a typical conventional practice,original solution to be processed is shown directed into the system atline 2, with pressure for driving solvent across a reverse osmosismembrane 3 of the reverse osmosis membrane unit 1 being applied by thereverse osmosis pump 5.

Permeate is shown being removed from the reverse osmosis membrane unit1, at line 7. The permeate, again, comprises the solvent which haspassed through the reverse osmosis membrane 3. The term “permeate”,then, for a given the reverse osmosis system, generally refers to aprocess off stream from the reverse osmosis membrane unit 1 which haspassed through the osmosis membrane 3 within the unit 1, and thus whichis increased in solvent concentration and reduced in soluteconcentration, relative to the inlet feed.

Concentrate is shown being removed from the reverse osmosis membraneunit at line 9. Concentrate in line 9 is original solution that has beenconcentrated with respect to the solute, as a result of the solventtransfer through the reverse osmosis membrane 3 within the unit 1.

At 10 a pressure reduction device such as: a valve system, a regulatorsystem or a regenerative pressure letdown turbine, is depicted in theline for the concentrate solution 9. Thus at 11 a concentrate line isdepicted, having a line pressure reduced from the reverse osmosis systemor unit pressure.

In FIG. 1, the reverse osmosis membrane unit 1 is depicted as it wouldbe when used in a typical reverse osmosis operation, generally involvinga single step.

Herein, line 12 will sometimes be referred to as the reverse osmosishigh pressure inlet (or feed) line. This is because line 12 is generallythe feed inlet to the reverse osmosis unit 1, under the pressure appliedby the reverse osmosis pump 5. Side 1 x of reverse osmosis membrane 3 issometimes referred to as the high pressure side of the reverse osmosismembrane or unit 1, since it is the side of the membrane unit 1receiving inlet feed (line 12) under the pressure of the reverse osmosismembrane pump 5. Line 9, the concentrate line from the reverse osmosisunit 1, is sometimes referred to as a high pressure side outlet line, orby similar terms.

Still referring to FIG. 1, line 7 is sometimes referred to as the lowpressure side outlet line, as it provides for flow of solvent from a lowpressure side 1 y of the reverse osmosis membrane 3 or unit 1.

In some instances, reverse osmosis units of the type described in FIG.1, have been applied in multi-stage (series, non-cascading) operations.An example of this is indicated in FIG. 2. Here, concentrate line 9 froma system in accord with FIG. 1 is directed through a reverse osmosispump 10 x for introduction into a high pressure side 15 x of a secondstage reverse osmosis unit 15, via a line 16. Line 16, then, is a highpressure side inlet line for reverse osmosis unit 15. At 17, aconcentrate line (or high pressure outlet line) from a high pressureside 15 x of reverse osmosis unit 15 is shown, directed through pressurereduction apparatus 18 to provide a concentrate line 11. At 19 a lowpressure side outlet line from low pressure side 15 y, of unit osmoticmembrane 15 z, is shown removing permeate which is then combined withthe permeate of line 7 at 20, providing a combined permeate line 21 fromthe process.

In general, it is common in reverse osmosis systems to use multiplestages, whereby concentrate discharged from a first stage membrane unitis directed and re-pressurized to feed through a second membrane, toachieve increased solvent extraction efficiencies. The concentratedischarge from the second membrane, i.e., line 17, is typically toohighly concentrated to be treated any further by reverse osmosis, sincethe operating pressures necessary would typically be too high for atypical membrane.

II. Improved Reverse Osmosis Membrane Unit and Reverse OsmosisTechniques; FIG. 2A

In FIG. 2A, a schematic depiction is provided for an improved reverseosmosis unit, for use with a system and techniques, in a solutionseparation process. Referring to FIG. 2A, reference numeral 25indicates, generally, the system and process. System 25 includes thereina reverse osmosis membrane unit 26, modified in accord with the presentdisclosure. More specifically, membrane unit 26 comprises membranearrangement or membrane 27 defining a high pressure side 27 a and a lowpressure side 27 b. Reverse osmosis unit 26 includes a high pressureside inlet line 28 and a low pressure side inlet line 29, a highpressure side (concentrate or concentrated solution) outlet 30 and a lowpressure side (dilute solution) outlet 31.

Reverse osmosis membrane unit 26, then, has been modified from reverseosmosis unit 1, 15, FIGS. 1 and 2, in that the reverse osmosis unit 26is provided with an inlet line to both the high pressure side 27 a andthe low pressure side 27 b. Thus, the reverse osmosis process conductedwithin the unit 26 is conducted between solutions on opposite sides ofthe membrane, 27, provided through inlet feed. Typically, disregardingpressure differential, the inlet feed to the high pressure side 27 a atline 28 will differ from the inlet feed of the low pressure side 27 b atline 29 by no more than 20% solute concentration, typically no more than15% solute concentration; and, usually no more than 10% soluteconcentration. Indeed in some applications and techniques describedherein, the concentration of solute in both the inlet feed to the highpressure side at 27 a and the inlet feed 29 to the low pressure side 27b will be the same solution (solute) concentration, but for pressuredifference and possible flow rate difference.

Stated in more general terms, the concentration differential between thesolutions on the high pressure side and low pressure side cannot be at alevel which is greater than a combination of typical pressuredifferentials for operation of the unit, without damage to the unit. Themaximum concentration differences as referenced above will be typical.

Examples of use of the reverse osmosis unit 26 are described hereinbelow, in connection with other figures. Before turning to those generaltechniques, further description of system 25, FIG. 2A is provided.

Referring to FIG. 2A, the original solution is shown directed into thesystem 25 through inlet line 32. The solution of line 32 is pressurizedat pump 33 to provide an inlet line 34 of pressurized original solution.Line 34 is directed to joint 34 a, where it is split into a first line34 b and a second line 34 c. The first line 34 b is directed to the highpressure side inlet line 28 for unit 26. Line 34 c is directed throughpressure reducer 35 to provide a line 36 directed into inlet line 29 tothe low pressure side 27 b.

Thus, for the particular, example, reverse osmosis process depicted asconducted in unit 26, high pressure side inlet feed 28 comprises thesame solution, with respect to solute concentration (disregardingpressure differential and possible flow rate) as the inlet feed at line29 to the low pressure side 27 b.

The concentrate outlet previously identified as being in line 30, isshown directed through pressure reducer 37 to provide concentrate outflow 38 from the system 25. It is noted that schematic depiction of unit26 provided in FIG. 2A, flow with respect to high pressure side inletfeed 28 and low pressure side inlet feed 29 are depicted as countercurrent through the unit 26. While this may be typical and preferred,alternate approaches are possible. By the term “counter current” andvariants thereof, in this context, it is meant that the inlet flow feedto the high pressure side is generally at or near an opposite end of themembrane unit, from an end of the membrane unit at or near which the lowpressure side inlet feed is provided.

In addition, as referenced above, for the particular example system 25depicted, the unit 26 is shown operated with inlet feed line 28 to thehigh pressure side that is the same, in solute concentrationdisregarding pressure differences, as the inlet feed line 29 to the lowpressure side 27 b. In some applications and techniques describedherein, as will apparent from descriptions below in connection withother figures, one or other, or both, of the inlet feeds (28, 29) can bemodified. However, in general even if modified, typical practicesaccording to the present disclosure, with units in accord with unit 26(having both a high pressure side inlet feed and a low pressure sideinlet feed) are conducted such that the two inlet feeds do not differfrom one another by more than 20% in solute concentration, usually nomore than 15% solute concentration; and, typically 10% soluteconcentration or less.

The reverse osmosis unit is generally in accord with unit 26 can beconstructed by using a conventional reverse osmosis unit, and providingfor the appropriate feed lines thereto. For example, a spiral woundreverse osmosis membrane obtained from GE Water and ProcessTechnologies, as previously described, can be modified such that a smalldiameter inner tube in which the permeate flows can be equipped withboth an inlet and outlet port, rather than only an outlet port.Alternate reverse osmosis membrane units and modules can be analogouslymodified or constructed.

III. Some Example Variations, FIGS. 2B-2F

In FIG. 2, an example system 1100 is depicted. Here a single reverseosmosis unit 26 is depicted, comprising a membrane arrangement ormembrane 27 defining a high pressure side 27 a and a low pressure side27 b. Solution into the system is shown at 32. At joint 32 x, the inletsolution is split into lines 32 a, 32 b. At pump 33, line 32 a ispressurized and directed into inlet feed 28, for the high pressure side27 a of unit 26. At 33 x, a low pressure pump for line 32 b is shown,providing a low pressure inlet feed at line 29, to low pressure side 27b of unit 26. As with the system of FIG. 2A, at line 31, dilute solutionout is provided. At line 30, a concentrate (solution) out is provided,directed through pressure reducer 37, to provide a final concentrate outline 38.

Comparing FIGS. 2A and 2B, then, in FIG. 2B the variation relates towhen in the process, a split forming two feeds is provided. In each casethe same feed, but for concentration and possibly flow rate, is providedto both the upstream and downstream sides of the reverse osmosis unitinvolved, i.e. unit 26.

In FIG. 2C, another variation is provided, again using a single reverseosmosis unit 26 comprising membrane arrangement 27 having a highpressure side 27 a and a low pressure side 27 b. At line 32, originalsolution feed into the system, designated generally at 1200 is provided.Pump 33 x provides for pressurization of the inlet feed. At joint 34 a,the feed is separated at a line 34 b and line 34 c. Typically, pump 33 xwill be a low pressure pump. Thus, it provides the appropriate pressurein line 34 c, for the low pressure side feed. At 33, a high pressurepump is provided, providing a line 34 x of high pressure. At joint 1201,the material in line 34 x is directed into an inlet side feed 28, fromthe high pressure side of unit 26. Also, at joint 1201, an optional feedfrom line 1202, directed from a membrane sweeping pump 1203 is provided.In particular, at line 1204, a portion of high pressure side outlet atline 30, directed from joint 1205 into line 1204 and membrane sweepingpump 1203. Thus, it is directed via line 1202 to joint 1201 and backinto reverse osmosis unit 26. At line 29, a low pressure side inlet feedis provided. At line 31, dilute solution out is provided. At 37 apressure reducer is provided, providing for a final concentrate outletline at 38.

Thus, the system of FIG. 2C is generally analogous to the system of 2B,except for: using low pressure pump 33 x upstream of joint 34 a; and,using a membrane sweeping pump 1203 and a bleed circuit from outlet line30 back into inlet line 28.

One common problem associated with processing higher and higher solutionconcentrations in a reverse osmosis system is the phenomenon of solutionconcentration gradients very near the membrane. This occurs as solventis forced out of the solution directly adjacent to the membrane wall,while portions of the solution stream farther away from the membranewhile still within the reverse osmosis membrane unit do not experienceas high of a concentration. As this thin layer of high concentrationforms near the membrane wall it has the net effect of increasing theosmotic pressure across the membrane due to the increased solutionconcentration being directly exposed to the membrane. This increasing ofosmotic pressure pushes back on the driving reverse osmosis pressurebeing applied to achieve a separation thereby reducing flux through themembrane for an overall applied driving pressure. This increase in-turnreduces the overall membrane effectiveness and/or increases pumpingenergy consumption to achieve the desired separation.

This localized area of high concentration near the membrane wall is alsoprone to reaching solution concentrations high enough to causeprecipitates to form as the upper solubility limit of the solute isreached for a given solution. If precipitate formation is occurring,these precipitates can quickly clog the minute pores of the RO (reverseosmosis) membrane reducing its effectiveness. In addition other processsolution contaminates that may be in the solution stream being processedwill have a tendency to build up on the membrane further reducing fluxthrough the membrane. To address these problems the traditional methodfor large scale RO units is to conduct periodic cleaning as a way ofremoving much of the materials clogging the micro pores in the membrane.This is often done by flushing the membrane with high velocity purgesand/or chemical based cleaning techniques.

To mitigate these problems a membrane sweeping pump could be utilized togenerate an increased rate of re-circulated flow across the membrane'supstream high pressure side, which is tangential to the membrane wallthereby sweeping precipitates and other potential contaminates along andthus reducing the likelihood of them clogging or otherwise fouling themembrane, as illustrated in FIG. 2C. This tangential sweeping actionwould also serve to breakdown the concentration gradient boundary layerphenomena described herein thereby potentially improving overall systemperformance, increasing membrane life, and/or increasing the timeintervals between required periodic membrane cleanings.

In FIG. 2D, a system using two reverse osmosis units is provided. Afirst unit 26 generally is analogous to the previous units 26 described,and comprises a membrane arrangement or membrane 27 having a highpressure side 27 a and a low pressure side 27 b. Inlet line 32 isdirected into low pressure pump 33 x. At joint 34 a, line 34 c comprisesa low pressure line, directed to inlet line 29 for reverse osmosis unit26. At 33, a high pressure pump is provided, increasing the inletpressure of the original solution from joint 34 a. This solution isdirected past joint 1301, to high pressure side inlet line 28. At 30, ahigh pressure side outlet is shown removed from unit 26, directed topressure reducer 37, to provide a concentrate outlet at 38. At 31, a lowpressure side outlet flow from unit 26 is shown directed through pump1302, to provide a high pressure side inlet feed at line 1303, to unit1305. Reverse osmosis unit reverse osmosis 1305 includes a membranearrangement or membrane 1306 having a high pressure side 1306 a and alow pressure side 1306 b. The particular unit 1305 depicted, does notinclude a low pressure side inlet feed. At 1310, a high pressure sideoutlet from unit 1305 is shown, directed into joint 1301. At 1331, afinal dilute solution outlet, from system 1300 is provided.

The unit of FIG. 2D, then, provides a second, polishing, reverse osmosisunit 1305 to capture some solute and direct it back into a high pressureside of unit 26, while at the same time providing a polished, mostdilute, system outflow at line 1331.

In FIG. 2E, a variation in the system of FIG. 2D, is depicted generallyat 1400. Referring to FIG. 2E, unit 26, as previously characterized,with a reverse osmosis membrane arrangement 27 having a high pressureside 27 a and a low pressure side 27 b. A second unit 1405, however,differs from FIG. 2D, in that unit 1405 not only has a high pressureside inlet 1403, a high pressure side outlet 1410, but it also includesa low pressure side inlet 1411. Thus, unit 1405 includes a membranearrangement 1406 having a high pressure side 1406 a and a low pressureside 1406 b, and both the high pressure side inlet 1403 and a lowpressure side inlet 1411. At 1431, a final dilute solution, outlet fromsystem 1400 is depicted.

Referring to FIG. 2E, original solution enters at 32. At 33 x, a lowpressure pump is provided. At joint 34 a, the low pressurized solutionis split into a low pressure line 34 c, and a line directed to line tohigh pressure pump 33. The pressurized solution from pump 33 is directedpast joint 1401, to high pressure side inlet line 28 for reverse osmosisunit 26. At 30, a high pressure side concentrate outlet from unit 26 isshown, directed to pressure reducer 37 to provide a concentrate outletline 38. At line 29, the low pressure solution line 34 c is directed aslow pressure side inlet solution to unit 26. At 31, the low pressureside, dilute solution, outlet from unit 26 is shown. This is directed tojoint 1408, where it split into line 1408 a and 1408 b. Line 1408 a isdirected through high pressure pump 1415 and into line 1403, the highpressure side inlet line for unit 1405. Line 1408 b, directed to inletline 1411 from the low pressure side of unit 1405.

Attention is now directed to FIG. 2F, which depicts the addition of athird reverse osmosis unit, to system 1400, for forming system 1500.Referring to FIG. 2F, the third unit is indicated generally at 1510,comprising a reverse osmosis membrane arrangement or membrane 1511having a high pressure side 1511 a and a low pressure side 1511 b.Referring to FIG. 2F, at 32, original solution is shown directed intosystem 1500. At 33 x, a low pressure pump is provided, directing thesolution to joint 34 a, where it is split into lines 34 c and 34 b. Atpump 33, a high pressure treatment is provided, to the material line 34b. It is directed through joint 1401, to inlet line 28 for reverseosmosis unit 26; unit 26 comprising a membrane arrangement 27 having ahigh pressure side 27 a and a low pressure side 27 b. At 30, a highpressure side (concentrate) outlet line from unit 26 is depicting,directing concentrate through reducer 37 to provide a concentrate outline 38. At 31, low pressure side outlet is directed to joint 1408.Here, it is split into line 1408 a and 1408 b. Line 1408 a is directedthrough high pressure pump 1415 past joint 1515, to provide an inletline 1403 for unit 1405; unit 1405 comprising a membrane arrangement1406 with a high pressure side 1406 a and a low pressure side 1406 b. Atline 1410, a high pressure side, concentrate, outlet is shown directingconcentrate from unit 1405 to joint 1401. At 1431, a low pressure sideoutlet, is shown directing liquid to joint 1516. It is noted that unit1405 includes a low pressure side inlet stream at 1411, comprising thefeed in line 1408 b.

Referring to joint 1516, the liquid is split into lines 1516 a and 1516b. At line 1516 a, is directed through high pressure pump 1520, toprovide high pressure side inlet feed at 1521, to reverse osmosis unit1510. Line 1516 b is directed to low pressure side inlet feed 1522 toreverse osmosis unit 1510. At 1530, a high pressure side, concentrate,outlet line from unit 1510 is shown, directing concentrate back to joint1515. At 1531, a final, dilute solution outlet from system 1500 isdepicted.

IV. Other Reverse Osmosis Systems and Processes A. General Principles

Herein, certain unique, progressively, cascading configurations ofreverse osmosis membrane units are described for use with an entirerange of solution concentrations, which would otherwise require reverseosmosis pressures typically in excess of those readily withstood bytypical osmotic membranes.

Cascading reverse osmosis techniques described herein are made possible,in part, through selected use of a reverse osmosis membrane unitanalogous to unit 26 in FIG. 2A (whether counter current flow orotherwise).

A feature of many cascading reverse osmosis system or process in accordwith the disclosures herein, is that the system at least includes:

(i) a first, final, concentrated solution generating reverse osmosisunit; and,

(ii) a first, final, dilute solution or solvent-generating reverseosmosis unit.

A feature of many cascading reverse osmosis system or process in accordwith the disclosures herein, is that the system may also include:

(iii) an intermediate reverse osmosis membrane unit system, comprisingone or more reverse osmosis units.

The term “final concentrate-generating reverse osmosis unit”, andvariants thereof is meant to refer to a reverse osmosis unit in thesystem, which provides the final, polished concentrate outlet flow fromthe system. In many systems there will be only one such unit, referredto herein as a “first” unit. However, in one system described herein,FIG. 5, there are two (i.e. first and second) finalconcentrate-generating reverse osmosis units.

The term “final, solvent-generating reverse osmosis unit” and variantsthereof, as used herein, is meant to refer to the reverse osmosis unitfrom which the final solvent stream (i.e. purified solvent or reducedsolute solvent) leaves the reverse osmosis membrane system characterizedherein. Typically, there is only one “final solvent-generating reverseosmosis unit”. However, principles characterized herein can be appliedwith more that one such units, for example in parallel. The term is notmeant to indicate whether the solvent is pure, or reduced in solutecontent but not pure.

In general, the intermediate reverse osmosis membrane unit systemcomprises one or more reverse osmosis units positioned generally in flowseries between: a final reduced-solute dilute solution orsolvent-generating reverse osmosis unit; and, a finalconcentrate-generating reverse osmosis unit, as characterized above.That is, low pressure side outlet flow from the finalconcentrate-generating reverse osmosis unit(s) is generally directedinto the intermediate system; low pressure side outlet flow from theintermediate reverse osmosis system is generally directed into the finaldilute solution generating reverse osmosis unit(s); concentrate from thefinal dilute solution or solvent-generating reverse osmosis unit(s) isgenerally directed into the intermediate system; and, concentrate fromthe intermediate system is generally directed into the finalconcentrate-generating reverse osmosis membrane unit(s). Within theintermediate system, the flow maybe in series, but other configurationsare possible.

A number of examples are described herein, including ones that have twoor more reverse osmosis membrane units, in the intermediate system. Insome examples described herein, there are five reverse osmosis membraneunits, in the intermediate system.

From the example systems described herein, general principles forapplication of the techniques described herein in a wide variety ofsystems can be understood.

The term “cascading” as used herein, generally refers to the fact thatwhen the system is operated, concentrate from the final reduced-solutesolvent-generating unit(s) is passed through the intermediate reverseosmosis unit system in flow-direction to the finalconcentrate-generating unit(s); and, low pressure side outlet flow fromthe final concentrate-generating reverse osmosis unit(s) is typicallydirected through the intermediate reverse osmosis unit system to thefinal solvent-generating reverse osmosis unit(s).

Of course, an original solution feed stream is directed into the system.It can be directed into one or more of: the final solvent-generatingreverse osmosis unit(s); the intermediate reverse osmosis unit system;and, the final concentrate-generating reverse osmosis unit(s), dependingon the system, and preference for operation.

Another typical characteristic of many systems and applicationsaccording to the present disclosure, is that at least each unit in theintermediate reverse osmosis unit system is operated with both a highpressure side inlet feed and a low pressure side inlet feed. Also, insome instances the first, final, concentrated solution-generatingreverse osmosis unit is operated with both a high pressure side inletfeed and a low pressure side inlet feed.

Further, for each selected unit having both a high pressure side inletfeed and a low pressure side inlet feed, within the intermediate reverseosmosis membrane unit system, the solute concentration of the highpressure side inlet stream and the low pressure side inlet streamtypically differs (if at all) by no more than 20%, usually no more than15%; and, often 10% or less. Indeed in some instances, the same inletfeed is provided to each of the high pressure side and the low pressureside of one or more selected reverse osmosis membrane units, in theintermediate reverse osmosis unit system. By this latter, it is notmeant that every reverse osmosis unit in the intermediate reverseosmosis membrane unit system necessarily has the same inlet and outletfeed as every other unit in the intermediate reverse osmosis membraneunit system. Rather, it is simply meant that each selected unit has thesame solute concentration in the high pressure side inlet feed and thelow pressure side inlet feed thereof.

It is also noted that a similar operation of the first, final,concentrated solution-generating reverse osmosis unit is sometimespracticed, i.e., where the solute concentration of the high pressureside inlet stream and the low pressure side inlet stream typicallydiffers (if at all) by no more than 20%, usually no more than 15%, andoften 10% or less. Again, in some instances the concentration in each ofthese two streams, for the first, final, concentratedsolution-generating reverse osmosis unit may be the same.

B. An Example System, FIG. 3.

In FIG. 3, at 40 an example cascading reverse osmosis system 40 isschematically depicted. Referring to FIG. 3, the system 40 includes, at41 a feed source of original solution to be processed. At 42, a firstprocess stream comprising a concentrated solute solution (concentrate)is shown being removed from the system 40. At 43 a final solvent processstream, of relatively low concentrate (i.e. relatively pure orreduced-solute) solvent (sometimes called dilute solution) is shown as asecond process stream from the system 40.

In general terms, the cascading reverse osmosis system 40 comprises aplurality of reverse osmosis units 47. In typical application, thereverse osmosis units 47 can be made from modifying commerciallyavailable units, and be generally identical to one another. Units suchas described above for unit 26, FIG. 2A can be used for those unitshaving both a high pressure side inlet feed and a low pressure sideinlet feed. For any unit that does not have both a high pressure sideinlet feed and a low pressure side inlet feed, a conventional,commercially available unit can be used. It is noted that the system 40depicted in FIG. 3, selected units having both a high pressure sideinlet feed and a low pressure side inlet feed are not shown with acounter current flow, but the techniques described can be implementedwith a counter current flow through such units, if desired.

In many applications of techniques described herein, a cascading system40 will include at least two (2) reverse osmosis units, typically atleast four (4), and for the particular configuration of FIG. 3 usuallyat least five (5) units although the number can be varied. The examplesystem 40 depicted, includes seven (7) reverse osmosis units 47, labeledA, B, C, D, E, F and G respectively.

In the terms used above, unit G is the first, final, dilute solution (orsolvent)-generating reverse osmosis unit, since it is the first unitwhich generates relatively purified solvent for process stream 43. UnitF is the first, final, concentrate-generating reverse osmosis unit,since it is the final unit that generates the concentrate stream 42.Units A, B, C, D and E, collectively, comprise the intermediate reverseosmosis membrane unit system.

Referring to FIG. 3, reverse osmosis unit A is the unit of theintermediate reverse osmosis unit system (units A-E, collectively) intowhich the feed solution of line 41 is first directed. Referring to FIG.3, original solution in the inlet line 41 is pressurized and conveyed,by reverse osmosis pump 49, into pressurized inlet line 50. At joint 51,the pressurized solution of line 50 is split, with a portion directed byline 51 x into high pressure side inlet line 53 for unit A, and with aportion directed by line 51 y through pressure reducer 54 into a lowpressure side inlet line 54 x, of reverse osmosis unit A.

From the above, an initial specific difference from the systems of FIGS.1 and 2 should be apparent. For the system of FIG. 3, reverse osmosisunit A is generally in accord with unit 26, FIG. 2A and has an inletfeed to both a high pressure side 55 x and a low pressure side 55 y ofmembrane arrangement 55. (Again, it is noted that unit A is not depictedin the figures in counter current flow, as is unit 26, FIG. 2A, howeverit could). For the systems of FIGS. 1 and 2, there was no inlet line tothe low pressure side of the reverse osmosis membrane units (1, 15)involved.

Within reverse osmosis unit A is provided an osmotic membranearrangement or membrane 55, with a high pressure side 55 x and a lowpressure side 55 y. It can be seen that within unit A, a reverse osmosisprocess is conducted with a portion of the mixture from line 50 providedto opposite sides of the membrane 55.

As will be understood from the descriptions below, typically the inletfeed to the high pressure side 55 x, is modified from a content of line50, as inlet feed is fed into the unit A. Typically concentration ofsolute within the inlet feed to opposite sides of membrane 55, does notdiffer by more than 20%, usually not more than 15%, and typicallydiffers by only about 10% or less. This is discussed further below. Itis again noted that this characteristic level of differences, inconcentration of feed to opposite sides of the membrane 55 in unit A, isa typical characteristic feature of various membrane units in theexample, (A-E) used in an intermediate reverse osmosis membrane unitsystem in the example cascading reverse osmosis process 40 according tothe present disclosure.

At 58 a high pressure side outlet (concentrate) line from osmosis unit Ais depicted. The line 58 would include concentrate from first osmosisunit A. For the system 40 depicted, this concentrate is directed intoreverse osmosis unit B.

The reverse osmosis unit B includes reverse osmosis membrane arrangement60 with a high pressure side 60 x and a, low pressure side 60 y.Concentrate 58 from the high pressure side 55 x of reverse osmosis unitA is directed into high pressure side inlet line 61 for reverse osmosismembrane unit B. If desired, pressure modification equipment (pump toincrease pressure or pressure reduction system) can be included in line61, to modify the pressure.

Within reverse osmosis unit B, a reverse osmosis process is conducted ona high pressure side inlet liquid containing at least in partconcentrate from line 58. In a typical application of a process inaccord with system 40, inlet feed in line 61 is modified fromconcentrate line 58, before it is introduced into first reverse osmosisunit B.

At line 63 a low pressure side outlet (reduced-solute fraction) streamfrom the osmosis membrane unit B is depicted. The low pressure sideoutlet (dilute) stream 63 is shown pressurized by pump 65 and directedinto a pressurized solution stream 66. That is, stream 66 includes lowpressure side outlet solution (reduced-solute fraction solvent) fromreverse osmosis unit B, pressurized via pump 65. The stream 66 isdirected into line 50, and is thus mixed with the original solution 41,before that mixture is directed to joint 51 for splitting. Thus,relatively purified solvent from unit B is directed, as part of thecascading process, into the inlet solution for both sides (high and lowpressure) of the membrane 55 in reverse osmosis unit A.

Still referring to FIG. 3, at 67 a high pressure side outlet stream,comprising relatively concentrated solute, from reverse osmosis membraneunit B is shown. The relatively concentrated solution or concentrate(line 67) from reverse osmosis unit B, for system 40, is shown directedvia line 68 into a high pressure side inlet line 69 for reverse osmosisunit C. Typically, for a process in accord with FIG. 3, the feed in line69, to reverse osmosis unit C, will be modified from the content of line68 before it is introduced into the reverse osmosis unit C. This isdiscussed further below.

Still referring to FIG. 3, the reverse osmosis unit C comprises areverse osmosis membrane arrangement or membrane 75 with a high pressureside 75 x; and, a low pressure side 75 y. The solution directed intomembrane unit C via line 69 is processed, with a low pressure sidedilute solution leaving the low pressure side 75 y via low pressure sideoutlet line 76.

Low pressure side dilute solution outlet flow (relatively pure solventcompared to the inlet solution to the reverse osmosis membrane unit i.e.reduced-solute fraction solvent solution) from reverse osmosis membraneunit C is shown directed via line 76, with pressurization provided byreverse osmosis pump 78, into pressurized line 79. The pressurized line79 is directed to joint 80, where it is split, with a first stream 80 xdirected into inlet line 61 and thus into the high pressure inlet side60 x of reverse osmosis unit B. The second split stream is directed byline 80 y into pressure reducer 81, and then into low pressure inletline 82 for reverse osmosis unit B. In general terms, then, the reverseosmosis process conducted in unit B is conducted with a liquid feed, tothe high pressure side 60 x, comprising a combination of: high pressureside outlet flow (concentrate) from unit A and low pressure side outletflow (dilute solution) from unit C; and, with a feed stream to a lowpressure side 60 y comprising dilute solution from unit C. Typically,the reverse osmosis unit B will be operated such that a concentrationdifference, in solute, between inlet flow to the high pressure side andinlet flow to the low pressure side of unit B is not greater than 20%,typically no greater than 15%, and is usually 10% or less.

Still referring to FIG. 3, attention is now directed to reverse osmosisunit D. Reverse osmosis unit D includes a reverse osmosis membranearrangement or membrane 90 with a high pressure side 90 x and lowpressure side 90 y. At 91 a high pressure side inlet (feed) line forreverse osmosis unit D is depicted.

For the particular process conducted in FIG. 3, at 59 a low pressureside (reduced-solute solvent) outlet flow from reverse osmosis membraneA is depicted. This outlet flow is pressurized at pump 94 and isdirected via pressurized line 95, to joint 96. Here low pressure sideoutlet flow from unit A, having been pressurized at pump 94, is splitinto a first line 96 x, which directs a portion of the flow from line 59to a high pressure side inlet line 91 of reverse osmosis unit D. At line96 y, a portion of the low pressure side outlet flow from reverseosmosis unit A, pressurized by pump 94, is directed through pressurereducer 97 into low pressure side inlet line 98, for reverse osmosisunit D.

From the above, it will be understood that in reverse osmosis unit D, areverse osmosis process is conducted between a high pressure sidesolution comprising a low pressure side outlet flow from unit A, and alow pressure side liquid feed also comprising low pressure side outletflow from unit A. Typically, the high pressure side inlet feed unit Dwill have been modified by addition thereto, of a further liquidmixture. However, typically the reverse osmosis process in unit D willbe conducted between initial high pressure side and low pressure sideinlet feed solutions differing in solute concentration by no more thanabout 20%, typically no more than 15%, and usually 10% or less.

At 99, a high pressure side outlet, or concentrate steam, from reverseosmosis unit D is depicted. Concentrate line 99 from the high pressureside 90 x of reverse osmosis membrane 90, in unit D, is shown directingconcentrate from reverse osmosis unit D into the inlet line 53 forreverse osmosis unit A. Thus, the inlet composition to reverse osmosisunit A includes: the original solution mixture from line 41; the lowpressure side outlet flow in line 66 from reverse osmosis unit B; and,the concentrate line 99 from reverse osmosis unit D. Further, the lowpressure side inlet feed to reverse osmosis unit A includes: originalsolution from line 41; and, a portion of the low pressure side outletflow in line 66 from reverse osmosis unit B.

Again, in general, the high pressure inlet feed to reverse osmosis unitA, via line 53, and the low pressure side inlet feed to reverse osmosisunit A, via line 55, are provided in a manner such that the differencein solute concentration between the two is preferably no greater than20%, usually no greater than 15%, and often 10% or less, with a highersolute concentration being in the high pressure side inlet feed.

Referring again to reverse osmosis unit D, line 100 comprises a lowpressure side outlet line i.e. reduced-solute (dilute solution) solventline, from reverse osmosis unit D. Within line 100, then, is contained arelatively low concentration solute mixture (i.e. a relatively highpurity solvent).

The solution in line 100, from a low pressure side 90 y of reverseosmosis unit D, is pressurized via pump 101 and is directed into line102. The pressurized solution of line 102 is directed to joint 103 wherethe liquid is split. A first line 103 x directs a portion of the liquidin line 102 into high pressure side inlet line 109 for reverse osmosisunit E.

Reverse osmosis unit E comprises a reverse osmosis membrane or membranearrangement 110 having a high pressure side 110 x and a low pressureside 110 y. Line 109, then, is an inlet feed line for a high pressureside 110 x.

Also at joint 103, line 103 y provides a portion of the pressurizeddilute solution from line 102, after passage through pressure reducer112 into low pressure side inlet line 113, for reverse osmosis unit E.

At 115, a concentrate line, or high pressure side outlet line, fromreverse osmosis unit E is shown. Within line 115 would be includedconcentrate, from a reverse osmosis process conducted in reverse osmosisunit E. For the particular example system 40 depicted, the concentratein line 115 is directed into high pressure side inlet line 91 for unitD. Thus, for the example system 40 shown, a reverse osmosis processconducted in unit D is conducted with a high pressure side inlet feedcomprising a combination of: pressurized low pressure side outlet flowfrom reverse osmosis unit A; and, pressurized concentrate from reverseosmosis unit E. The low pressure side of unit D is provided with aninlet liquid comprising low pressure side outlet flow from unit A. Thedifference, then, in the solutions on opposite sides of the membrane 90in unit D, where the reverse osmosis process is conducted, is adifference provided by the inclusion of the concentrate from unit Ewithin the high pressure side inlet line 91.

In a typical process according to FIG. 3, the reverse osmosis unit D isoperated with a concentration difference between the high pressure sideinlet feed and the low pressure side inlet feed, with respect to soluteconcentration, of no greater than 20%, usually no greater than 15%, andoften 10% or less, with a higher solute concentration being on the highpressure side of the reverse osmosis membrane unit D.

Still referring to FIG. 3, and process 40, at 116 a low pressure sideoutlet line 116, from unit E, is depicted. Alternately stated, withinline 116 is provided low pressure side dilute solution from the reverseosmosis unit E. The solution would comprise relatively purified solvent(a relatively low concentrate, i.e. dilute, solute) from the unit E.

For the particular system 40 and process depicted, flow from line 116,i.e., low pressure side outlet flow from unit E, is further polished.This is conducted with pressurization at pump 118, directing thepressurized flow via line 119 into reverse osmosis unit G, used as apolishing unit. The reverse osmosis unit G has a reverse osmosismembrane or membrane arrangement 120, with a high pressure side 120 xand a low pressure side 120 y. Line 119 serves as a high pressure inletline to unit G. At 43, a polished, low pressure side, solvent or lowpressure side outlet flow is depicted. At 121, high pressure sideconcentrate outlet line 121 is depicted. The process conducted in theexample unit G, then, does not involve an inlet feed to the low pressureside 120 y. For the particular example process of FIG. 3, theconcentrate line 121, from unit G, is included within the inlet solutionat line 109 for the high pressure side 110 x of reverse osmosis unit E.

The operation conducted (in the example depicted) in reverse osmosisunit E is a reverse osmosis operation across the membrane 110 betweenhigh pressure side inlet feed solution of a mixture of: concentrate fromunit G; and, low pressure side outlet flow from unit D; and, a lowpressure side inlet at 113 comprising low pressure side outlet flow fromunit D.

In a typical operation, the reverse osmosis unit E is conducted with asolute concentration difference, between the high pressure side and thelow pressure side, of no greater than about 20%; typically no greaterthan 15%, and preferably 10% or less, with a solute concentration beinggreater on the high pressure side.

For the particular process depicted in FIG. 3, a final concentratingstep is also conducted on a portion of the concentrate from reverseosmosis unit C. The concentrate from unit C is depicted leaving unit Cvia line 77. This concentrate is shown split at joint 130 into a firstpressurized inlet line 130 x for reverse osmosis unit F; and, a secondline 130 y, shown directing a portion of the concentrate from line 77 topressure reducer 131, and ultimately to inlet line 133, a low pressureside inlet line, for reverse osmosis unit F.

Reverse osmosis unit F includes the reverse osmosis membrane or membranearrangement 140 having a high pressure side 140 x and a low pressureside 140 y. Concentrate is shown leaving the high pressure side reverseosmosis unit F, via high pressure side outlet line 150. This concentrateis reduced in pressure at reduction unit 151, and comprises theconcentrate out of process 40 via line 42.

At 155, a low pressure side outlet line from reverse osmosis unit F isdepicted. Within line 155 would be low pressure side flow (dilutesolution), from reverse osmosis unit F. This flow (dilute solution) isshown pressurized at pump 156 and then directed into pressurized line157 to joint 158. At joint 158 low pressure side outlet flow fromreverse osmosis unit F is split to a first line 158 x, which directs aportion of the flow into the high pressure side inlet line 69 forreverse osmosis unit C. Second line 158 y, from joint 158, directs aportion of the flow from line 157 to pressure reducer 159 and ultimatelyinto low pressure side inlet line 160 for reverse osmosis membrane unitC. Thus, the reverse osmosis operation conducted in unit C is between ahigh pressure side liquid comprising: a mixture of low pressure sideoutlet flow from unit F and concentrate from unit B; and, low pressureside liquid comprising low pressure side outlet flow from unit F.

In a typical arrangement, the first osmosis unit C is operated with aconcentration difference, in solute, between the high pressure sideinlet feed and the low pressure side inlet feed, of no greater than 20%,usually no greater than 15%; and typically and preferably no greaterthan 10%. The (relatively) higher solute concentration typically isprovided on the high pressure side.

To summarize the process conducted in the system depicted in FIG. 3, anoriginal liquid/solute feed solution to be processed enters the system41, and is conveyed and pressurized in reverse osmosis pump 49 toconduit 50.

In general terms, it can be seen that system 40 includes:

(a) concentrate flow from the first, final, dilute solution-generatingunit G into an intermediate reverse osmosis membrane unit system (theexample comprising units A-E);

(b) concentrate flow from the intermediate reverse osmosis membrane unitsystem (the example, comprising units A-E) into the first, final,concentrate-generating reverse osmosis membrane unit F;

(c) low pressure side outlet flow (reduced-solute solvent or dilutesolution) from the first, final, concentrate-generating reverse osmosisunit F into the intermediate reverse osmosis membrane unit system (theexample units E, D, A, B and C); and,

(d) low pressure side outlet flow (reduced-solute solvent or dilutesolution) from the intermediate reverse osmosis membrane unit system (inthe system 40 comprising units A-E) to the final dilute solution (orsolution)-generating reverse osmosis unit G.

More specifically, the system 40 according to FIG. 3, includes: first,final, solvent (or dilute solution)-generating reverse osmosis unit G;first, final, concentrate-generating reverse osmosis unit F; and, anintermediate reverse osmosis unit system comprising one or more reverseosmosis units, typically at least two, sometimes at least three; and, inthis example specifically, five units. In the system of FIG. 40, thefive units (A-E) of the intermediate reverse osmosis unit system arearranged is series flow order with respect to: concentrate flow from thefinal solvent or dilute solution-generating reverse osmosis unit Gultimately to the final concentrate-generating reverse osmosis unit F(the series being E-D-A-B-C); and, low pressure side outlet flow,(reduced-solute solvent or dilute solution flow) from the finalconcentrate-generating reverse osmosis unit F ultimately to the finalsolvent or dilute solution-generating reverse osmosis unit G (the seriesbeing C-B-A-D-E).

For the particular example system 40 depicted, the intermediate reverseosmosis membrane unit system, (for the example shown comprising unitsA-E) can be further characterized as including: a most permeateflow-direction reverse osmosis unit, unit E; a most concentrateflow-direction reverse osmosis unit, unit C; and, at least one centralunit, the example including depicted three central units (A, B and D).

For the example system depicted, the original inlet solution is directedinto a central unit (one of the units A, B and D) of the intermediatereverse osmosis unit system (units A-E). For the specific example, thisinlet direction is into central unit A.

The cascading effect, then, is readily viewable. Cascading solventpurification (solute reduction) occurs in flow from the first, final,concentrate-generating reverse osmosis unit (F) to the first, final,dilute solution (or solvent)-generating reverse osmosis unit G. Soluteconcentration (concentrate) occurs in flow from the first, final, dilutesolution or solvent-generating reverse osmosis unit G to the first,final, concentrate-generating reverse osmosis unit F. The inlet feed(line 41) is directed into system 40 at a selected location where it canjoin this cascading process, desirably. Alternative locations oforiginal solution introduction are possible.

It is noted that herein, in some instances unit B will be referred to asthe next most permeate flow-direction reverse osmosis unit, to reverseosmosis unit C; reverse osmosis A will be referred to as the second nextpermeate flow-direction reverse osmosis unit, to reverse osmosis unit C;and, reverse osmosis unit D will be referred to as a third next permeateflow-direction reverse osmosis unit, to reverse osmosis unit C.Analogously, reverse osmosis unit D may be referred to as the first nextconcentrate flow-direction reverse osmosis unit, to reverse osmosis unitE; reverse osmosis unit A may be referred to as the second nextconcentrate flow-direction reverse osmosis unit, to reverse osmosis unitE; and, reverse osmosis unit B may be referred to as a third nextconcentrate flow-direction reverse osmosis unit, to reverse osmosis unitE. (Herein, these terms are meant to refer to schematic flow directions,not physical location).

In some instances, herein flow may be referred to as “ultimate” or byvariants thereof. For example concentrate flow from unit G may becharacterized as ultimately directed to unit F. By this (and withoutmore) it is meant that the concentrate from unit G is either directeddirectly into unit F, or ultimately therethrough by passage throughother units. When the term “directly” is used herein, with respect tocharacterizing flow, it is meant that flow from one unit is directed toanother unit, without passage through an intermediate unit.

In system 40, FIG. 3, a variety of pumps, pressure reducers, and jointlocations are shown. It should be understood that alternatives fromthese specifics can be used, in accord with applications of thetechniques described in FIG. 3.

It is noted that in FIG. 3, a number of phantom arrowheads aredesignated by the reference “r”. These indicate that under someprocessing conditions, the flow in the identified line may be in thedirection indicated by the arrowhead “r”. This will depend, of course,upon the overall operating conditions for the system.

C. Another Example System, FIG. 4

Attention is now directed to FIG. 4, in which another example system isdepicted, at 200. Referring to FIG. 4, original solution is shownentering the system at 201, with a concentrate line out at 202 and a(dilute solution) solvent outlet line out 203. The system of FIG. 4, isoperated with seven reverse osmosis units indicated at H, I, J, K, L, M,and N, respectively. Reverse osmosis system 200 is operated, in someways, analogously to system 40, FIG. 3. However, modifications in linedirection and splitting are made for convenient and efficient operation,in certain applications.

Referring to FIG. 4, the original solution feed mixture at line 201 isdirected to pump arrangement 205, and into pressurized inlet line 206.Line 206 is directed to joint 207 where the inlet feed is split intoline 207 x and 207 y. Inlet line 207 x is directed into osmosis unit H,under pressure. In particular, reverse osmosis unit H comprises areverse osmosis membrane arrangement or membrane 210 having a highpressure side 210 x and a low pressure side 210 y. High pressure sideinlet 207 x is directed to the high pressure side 210 x. Line 207 y isdirected through pressure reducer 212, and then to inlet line 213 forlow pressure side 210 y. A reverse osmosis operation conducted in unitH, provides for a high pressure side concentrate outlet flow at line 215and low pressure side dilute solvent outlet flow at line at 216. Theconcentrate outlet flow at line 215, is the high pressure side outletflow from unit H. It is directed via line 217 through joint 218 to joint219. At joint 219, it is split into lines 219 x and 219 y. Line 219 x isa high pressure side inlet line for unit J. Line 219 y is directedthrough pressure reducer 220 to provide low pressure side inlet line 221for reverse osmosis unit J.

Reverse osmosis unit J comprises a reverse osmosis membrane arrangementor membrane arrangement 220 having a high pressure side 220 x and a lowpressure side 220 y.

From the low pressure side 220 y, dilute solution outlet line 225 isdepicted, directed through reverse osmosis pump 226 to provide a highpressure line 227 of low pressure side outlet flow (dilute solution)from reverse osmosis unit J. The flow of line 227 is directed to joint228 and then into line 229 to joint 230, where it is split into twolines, 231 and 232, while being directed to reverse osmosis unit I.

Reverse osmosis unit I includes reverse osmosis membrane or membranearrangement 240 having a high pressure side 240 x and a low pressureside 240 y. Line 231 is directed as an inlet, to high pressure side 240x. Line 232 is directed through pressure reducer 241, to provide aninlet line 242 to low pressure side 240 y of reverse osmosis unit I.

At 245, a low pressure side outlet solution is shown leaving lowpressure side 240 y of reverse osmosis unit I. The flow 245 is directedthrough reverse osmosis pump 246, providing a high pressure stream 247of low pressure side outlet from reverse osmosis unit I. This outlet orsolution is directed to joint 248, a joint with line 206, where thesolution of line 247 is combined with at least the original solution inline 206, to then be directed to joint 207, to split into lines 207 x,207 y as previously described.

Thus, from the above, it can be seen that reverse osmosis unit H isconducted with a liquid line to each of the high pressure and lowpressure sides, each of which at least includes: original feed solutionfrom line 206, and, low pressure side outlet flow from another reverseosmosis unit in the system 200, in this instance reverse osmosis unit I.As will be seen from the discussion below, an additional modifying inputis provided to joint 207.

Still referring to FIG. 4, in the system 200, at 250, a high pressureside (concentrate) outlet line from reverse osmosis unit I is shown.Line 250 directs the concentrate from reverse osmosis unit I to joint251, where it is split into lines 251 x and 251 y. Line 251 x isdirected as a high pressure side inlet stream, to reverse osmosis unitK. Reverse osmosis unit K comprises a reverse osmosis membrane ormembrane arrangement 255 having a high pressure side 255 x and lowpressure side 255 y.

Line 251 y, from joint 251, directs a portion of concentrate line 250,through pressure reducer 256 to line 257, which operates as a lowpressure side inlet liquid flow to reverse osmosis unit K.

Reverse osmosis unit K, then, acts as a final concentrate-generatingreverse osmosis unit, for concentrate in system 200. Liquid on oppositesides of the membrane 255 is the same, in each case concentrate from aprevious reverse osmosis unit, in this example instance, reverse osmosisunit I. At line 260 a high pressure side concentrate is shown removedfrom a reverse osmosis unit K. At 261 it is joined with line 262, a highpressure side concentrate line from as another finalconcentrate-generating reverse osmosis unit J. The combined concentrateis directed through pressure reducer 263, to provide concentrate out inline 202 from process 200.

Line 270 is a low pressure side outlet line from reverse osmosis unit K.It is directed through reverse osmosis pump 271 into line 272. At joint218 line 272 is joined with a concentrate line 215, and is directed tojoint 219, where the combined lines are split to be directed intoreverse osmosis unit J. Thus, the reverse osmosis process conducted inunit J is conducted with the same liquid (in solute concentration) onopposite sides of the membrane 220, that liquid comprising a combinationof concentrate from reverse osmosis unit H and low pressure side diluteoutlet flow from reverse osmosis unit K.

Still referring to FIG. 4, in system 200, at pump 280, low pressure sideoutlet line 216 from reverse osmosis unit H is pressurized, and isdirected through line 281 to joint 282. At joint 282, the liquid issplit into lines 282 x, 282 y. Line 282 x provides a high pressure inletto reverse osmosis unit L.

Reverse osmosis unit L, generally, includes a reverse osmosis membranearrangement or membrane 290 with a high pressure side 290 x and lowpressure side 290 y. Line 282 x provides direction of low pressure sideoutlet flow (dilute solution) from reverse osmosis unit H into highpressure side 290 x of reverse osmosis unit L. Line 282 y is directedinto pressure reducer 291, to provide line 292 as an inlet line to thelow pressure side 290 y of reverse osmosis unit L. Thus, it can be seenthat the reverse osmosis process conducted in reverse osmosis unit L isconducted with the input on opposite sides of the membrane 290 being thesame, i.e. each side being provided with low pressure side outlet fromreverse osmosis unit H.

At 295, a concentrate outlet from the high pressure side 290 x ofreverse osmosis unit L is shown. Line 295 directs the concentrate fromreverse osmosis unit L to joint 228, where it is combined with a dilutesolution in line 227, and is directed to joint 230. Thus, the reverseosmosis process conducted in reverse osmosis unit I is conducted withthe same liquid feed concentration to opposite sides of the membrane240, that liquid comprising a combination of low pressure side outlet(dilute solution) from one reverse osmosis unit membrane, in thisinstance reverse osmosis unit J; and, concentrate from another reverseosmosis unit, in this instance reverse osmosis unit L.

With respect to reverse osmosis unit L, attention is now directed toline 296, a low pressure side outlet line form reverse osmosis unit L.The solution in line 296 is pressurized at reverse osmosis pump 296 xand is provided in line 297 as a high pressure solution from a lowpressure side of reverse osmosis unit L. Line 297 is directed to joint298, where the solution in line 297 is combined with another liquid,discussed below, and is directed through line 299 to joint 300, wherethe liquid is split into lines 300 x, 300 y. Line 300 x comprises a highpressure side inlet line to reverse osmosis unit M.

Reverse osmosis unit M comprises a reverse osmosis membrane or membranearrangement 310 with the high pressure side 310 x and a low pressureside 310 y. Line 300 y is directed through pressure reducer 311 into312, line 312 being a liquid inlet line to the low pressure side 310 yof reverse osmosis unit M.

Line 320 is a high pressure side outlet line for reverse osmosis unit M,and carries concentrate from a reverse osmosis operation conductedwithin reverse osmosis unit M. Via line 320, this concentrate isdirected to joint 248 and is combined with pressurized outlet from a lowpressure side reverse osmosis unit I and original solution in line 206,to be directed to reverse osmosis unit H. Thus, the reverse osmosisprocess conducted within reverse osmosis unit H is not only conductedwith the same liquid on opposite sides of the membrane 210, but thatliquid comprises a combination of: the original feed line 206,pressurized low pressure side (dilute) outlet from reverse osmosis unitI; and, pressurized concentrate from reverse osmosis unit M.

At line 321, low pressure side outlet (dilute solution) from reverseosmosis unit M is provided. The solution is pressurized by reverseosmosis unit pump 322 and directed via line 323 into a final polishingreverse osmosis unit N. The reverse osmosis unit N comprises a reverseosmosis membrane or membrane arrangement 330 having a high pressure side331 and a low pressure side 332. Line 323 provides a high pressure sideinlet flow to reverse osmosis unit N. At 331, a high pressure sideoutlet, or concentrate outlet, for reverse unit N is shown. Via line331, this concentrate is directed to joint 298, where it is combinedwith pressurized solution in line 297 from a low pressure side ofreverse osmosis unit H, and is directed to joint 300. Then, the combinedliquid is split and directed into reverse osmosis unit M. Thus, thereverse osmosis operation conducted in reverse osmosis unit M isconducted with the same liquid concentration on opposite sides of themembrane 310. The liquid directed into opposite sides of membrane 310,then, of unit M, comprises a combination of: high pressure side outletconcentrate solution from unit N and low pressure side outlet dilutesolution from unit L.

Low pressure side outlet (permeate) from reverse osmosis unit Ncomprises purified solvent (dilute solution) directed out from system200 via line 203.

Directing attention again to reverse osmosis unit N, the solventpolishing unit from system 200, it is noted that reverse osmosisoperation conducted in reverse osmosis unit N is conducted with no inletfeed line to the low pressure side 322, and comprises a final polishingoperation conducted in general accord with reverse osmosis processdescribed above, in connection with FIG. 1. However, because theconcentrate inlet at line 323 comprises relatively pure solvent, thepolishing is readily conducted without the need for a relatively highpressure operation.

In general, the reverse osmosis processes conducted in system 200 areconducted with the same solution (in concentration solute) directed toboth the high pressure and low pressure side of each reverse osmosismembrane unit, except for the final permeate polishing unit N.

It is noted that the process conducted in the system of FIG. 4 can beoperated with a variety of alternate locations for pumps, pressurereducers and joints.

In the general terms characterized herein above, system 200 includes: afirst, final, solvent-generating reverse osmosis unit N; a first, final,concentrate-generating reverse osmosis unit J; a second finalconcentrate-generating reverse osmosis unit K; and, an intermediatereverse osmosis membrane unit system comprising a plurality of units, inthe example shown units M, L, H and I. In the example system 200depicted, the intermediate reverse osmosis unit membrane system (in theexample comprising units M, L, H and I) can be characterized asincluding: a most permeate flow-direction reverse osmosis unit M, afirst subsystem comprising reverse osmosis unit H; and, a secondsubsystem comprising two reverse osmosis units, in this instance asecond reverse osmosis unit L and a third reverse osmosis unit I.

In general, operation of reverse osmosis system 200 is as follows:

(a) concentrate from first, final, solvent (or dilutesolution)-generating reverse osmosis unit N is directed into the mostpermeate flow-direction reverse osmosis unit M of the intermediatereverse osmosis membrane unit system (units M, L, H and I,collectively).

(b) Concentrate outlet flow from the most permeate flow-directionreverse osmosis unit (M) in the intermediate reverse osmosis membraneunit system (units M, L, H and I) is directed into the first reverseosmosis unit H of the first subsystem.

(c) Concentrate outlet flow from the first reverse osmosis unit H of thefirst subsystem, is directed into the first, final,concentrate-generating reverse osmosis unit J.

(d) Low pressure side outlet flow (dilute solution) from the mostpermeate flow-direction reverse osmosis unit M of the intermediatesystem is directed to the first, final, solvent (or dilutesolution)-generating reverse osmosis unit N.

(e) Low pressure side outlet flow (dilute solution) from the first unitH of the first subsystem, is directed into the second unit L of thesecond subsystem units L and I.

(f) Low pressure side outlet flow (dilute solution) from the second unitL of the second subsystem L, I is directed to the most permeateflow-direction unit M of the intermediate reverse osmosis membrane unitsystem (units M, L, K, H and I, collectively).

(g) Concentrate from the second unit L in the second subsystem, isdirected into the third unit I of the second subsystem.

(h) Low pressure side outlet flow (dilute solution) from the third unitI of the second subsystem (units I and L) is directed into the firstunit H of the first subsystem, unit H; and, concentrate from the thirdunit I of the second subsystem (units I and L) is directed into thesecond, final, concentrate-generating reverse osmosis unit K.

(i) Further, for the example depicted, low pressure side outlet flow,from the second, final concentrate-generating reverse osmosis unit K isdirected into the first, final, concentrate-generating reverse osmosisunit J.

Flows to opposite sides of the various units (where relevant) aregenerally as depicted in FIG. 4 and characterized above.

D. A Further Example System, FIG. 5.

The systems described herein can be implemented in an overall equipmentsystem configured for parallel operation. An example is depicted in FIG.5. Referring to FIG. 5, a reverse osmosis system 400 is depicted. Asystem 400 has an original solution feed line 401, a concentrate outletline 402 and a solvent outlet line 403. In general, the system 400comprises two systems analogous to system 40, configured in parallel; inparticular, systems 40 x and 40 y. Each of units 40 x and 40 y cangenerally be the same as unit 40, FIG. 3, previously described, eachhaving seven (7) reverse osmosis units A-G, conducted in an operationsimilar to the description for unit 40, FIG. 3. In particular, inletline 401 is pressurized at pump 405 and then is directed to joint 410,where it is split into a first feed line 411 x, to system 40 x, and asecond feed line 411 y, to system 40 y. The concentrate outlet from unit40 x is shown as 420 x combined to joint 421 with concentrate outlet inline 420 y, from system 40 y, for overall concentrate out at line 402.

Solvent out from unit 40 x at line 430 x is combined with solvent outfrom unit 40 y at line 430 y, the combination occurring at joint 431,providing combined solvent out at line 403 from system 400.

Thus, system 400 generally comprises two systems corresponding to system40, FIG. 3, operated in parallel, the inlet line 401 being split fordirecting inlet to each system (40 x, 40 y) and the solvent andconcentrate outlet from each system being combined, to provide anoverall concentrate outlet 402 and solvent outlet 403. It is noted thatsuch an operation in parallel can be conducted with any of the systemsdescribed herein. Further, the principles can be applied with more thantwo operated systems in parallel.

Again, one of the other more common problems associated with processinghigher and higher solution concentrations via a reverse osmosis systemis the phenomenon of solution concentration gradients near the membrane.This occurs as solvent is forced out of the solution directly adjacentto the membrane, while portions of the solution stream farther away fromthe membrane do not experience as high of a concentration. Thislocalized area of high concentration tends to build over time. As thisthin layer of high concentration forms near the membrane wall it has thenet effect of increasing the osmotic pressure across the membrane due tothe increased solution concentration being directly exposed to themembrane. This increasing of osmotic pressure pushes back on the drivingreverse osmosis pressure being applied to achieve a separation therebyreducing flux through the membrane for a given pressure. This increasein-turn reduces the overall membrane effectiveness and/or increasespumping energy consumption to achieve the desired separation.

This localized area of high concentration near the membrane wall is alsoprone to reaching solution concentrations high enough to causeprecipitates to form as the upper solubility limit of the solute isreached for a given solution. These precipitates can quickly clog theminute pores of the RO membrane reducing its effectiveness. To addressthis problem and to remove other process solution contaminates, largescale RO units require periodic cleaning as a means removing much of thematerials clogging the micro pores in the membrane. This is often doneby flushing the membrane with high velocity purges and/or chemical basedcleaning techniques.

Several studies have been conducted which indicate that effective“cleaning” or regenerating of RO membranes can be achieved byperiodically operating them in a reverse flow pattern to their normaloperation. For example if a reverse osmosis membrane were to be operatedas a forward osmosis membrane thereby momentarily reversing thedirection of permeate flux through the membrane, this change of flow caneffectively backwash the membrane of accumulated micro-pore cloggingcontaminates. It is envisioned that this periodic forward osmosistechnique can be utilized in the present invention as a means ofcleaning and/or regenerating or rejuvenating the membranes to regainmuch of their efficiency as it degrades over time. This regenerationprocess can be combined with a high velocity flushing process in thepresent invention to effectively sweep solid contaminates away from themembrane to prevent rapid re-contamination of the membrane after abackwashing. This backwashing can be done when the system is temporarilyoff-line, or as an alternative, a separate parallel embodiment of thesystem can be utilized that would enable one unit to be online while theother unit is offline during a periodic backwashing process. Any numberof parallel embodiments of the system can be utilized in this way suchthat one or more membranes can be going through a cleaning cycle whileother parallel membrane units remain online and in operation.

It is noted that in FIG. 5 a number of phantom arrowheads are indicatedby the designation “r”. These are intended to indicate that the flows inthe identified lines can be in a reverse direction, i.e., in thedirection indicated by the arrowhead “r” under certain operatingconditions. This will be a matter dependent upon the particular choiceof operation selected by an operator for the system.

E. Another Example System, FIG. 6.

Attention is now directed to FIG. 6, in which another example system isdepicted, at 500. Referring to FIG. 6, an original solution is directedinto the system 500 via line 501. A process concentrate out line fromsystem 500 is shown at 502; and, a processed dilute solution out linefrom system 500 is shown at 503.

A system in accord with FIG. 6 generally includes at least two (2) andtypically at least three (3) reverse osmosis units, usually at leastfour (4). The particular example system 500 depicted includes sixreverse osmosis units A-F, respectively.

Referring to FIG. 6, an original solution feed in line 501 is directedthrough pump 510 into line 511. Line 511 is directed to joint 512, whereit is split into lines 513, 514, for direction in reverse osmosis unitA. Reverse osmosis unit A comprises a reverse osmosis membranearrangement or membrane 515 having a high pressure side 515 x and a lowpressure side 515 y. Line 513 is directed to inlet line 516, to highpressure side 515 x; and, inlet line 514 is directed through pressurereducer 517 into low pressure inlet line 519, for low pressure side 515y. It is noted that inlet feed line 511 is modified before reachingjoint 512, by including therein a low pressure side outlet line fromunit B, as described below. Further, at inlet line 516, liquid inletline 513 is modified by inclusion of a concentrate line from unit E,before introduction to reverse osmosis unit A. Thus, different specificliquids, in total, are directed into the high pressure side 515 x andlow pressure side 515 y to reverse osmosis unit A. The soluteconcentration difference between the inlet feeds 516, 519, if any, willtypically not be more than 20%, usually not more than 15% typically 10%or less.

An outlet line 520 from the high pressure side 515 x of reverse osmosisunit A is a concentrate outlet line. It is directed into inlet line 521for reverse osmosis unit B. It is noted that before entering reverseunit B, liquid in inlet line 520 is modified, at inlet line 521, byreceiving a portion of a low pressure side outlet flow from unit C, asdiscussed below.

Reverse osmosis unit B includes a reverse osmosis membrane arrangementor membrane 525 and has a high pressure side 525 x and low pressure side525 y. Within reverse osmosis unit B, a reverse osmosis operation isconducted including, a feed introduced into the high pressure side 525x, which comprises in part concentrate from reverse osmosis unit A, inthis instance mixed with low pressure side outlet from reverse osmosisunit C. Further the inlet feed in line 527, to low pressure side 525 yof reverse osmosis unit B, comprises low pressure outlet flow fromreverse osmosis unit C, as discussed below.

At line 530, a low pressure outlet (dilute solution) flow for reverseosmosis unit B is provided. The low pressure outlet flow for reverseosmosis unit B is directed through pump 531 into line 532. The lowpressure side outlet flow from reverse osmosis unit B, is mixed with theoriginal solution, pressurized in line 511, at joint 533. This mixedsolution is then directed to joint 512, to be split and directed, in duecourse, into unit A.

Line 540 is a high pressure side concentrate, outlet from reverseosmosis unit B. Line 540 is directed to inlet line 541 for reverseosmosis unit C.

Reverse osmosis unit C comprises a reverse osmosis membrane arrangementor membrane 545 having a high pressure side 545 x and a low pressureside 545 y. The reverse osmosis unit operation conducted in unit C, isbetween a high inlet pressure side feed inlet 541 that comprisesconcentrate from unit B, via line 540 and low pressure side outlet flowfrom reverse osmosis unit D, as discussed below. The low pressure sideinlet for reverse osmosis unit C, provided at line 546, generallycomprises low pressure side outlet flow from reverse osmosis unit D,again as discussed below.

Line 550 is a high pressure side concentrate outlet line from reverseosmosis outlet unit C. The liquid in line 550 is split at joint 551 witha first line 552 providing a high pressure side inlet line to reverseosmosis unit D; and, a second line 553 being directed through pressurereducer 554 to provide an inlet line 555 to a low pressure side ofreverse osmosis unit D.

In general, reverse osmosis unit D comprises a reverse osmosis membranearrangement or membrane 556 having a high pressure side 556 x and a lowpressure side 556 y. For the particular system 500 depicted, reverseosmosis unit D is a final polishing unit for concentrate. Line 560 is ahigh pressure side concentrate outlet from unit D directed throughpressure reducer 561, to provide concentrate outlet in line 502. Line562, is a low pressure side outlet flow (dilute solution) from reverseosmosis unit D. Line 562 is directed through pump 563 into line 564.Line 564 is directed to joint 565 where it is split into lines 566, 567.Line 566 is directed to joint 568, where it is combined with concentrateinlet line 540, to provide an inlet feed at line 541 for reverse osmosisunit C. Line 567 is directed through pressure reducer 570, to line 546,and provides a low pressure side inlet to reverse osmosis unit C. Thus,the reverse osmosis operation conducted in unit C is between a highpressure side inlet liquid at line 541 comprising a combination ofconcentrate from unit B and low pressure side outlet from unit D,whereas the low pressure side of unit C is provided with inletcomprising low pressure side outlet from unit D.

At line 575, a low pressure side outlet (dilute solution) from unit C isprovided. This solution is directed through pump 576, into line 577.Line 577 is directed to joint 578 where it is split into lines 579, 580.Line 579 is directed to joint 581, where the liquid is combined withliquid in line 520, to provide high pressure side inlet feed 521 toreverse osmosis unit B. Thus, the high pressure side inlet feed 521 toreverse osmosis unit B comprises a combination of: concentrate in line520 from reverse osmosis unit A; and, low pressure side outlet flow inline 579, from reverse osmosis unit C. The inlet line at 527, forreverse osmosis unit B low pressure side 525 y, comprises low pressureside outlet (dilute solution) from reverse osmosis unit C, from line 580after passage through pressure reducer 526.

Still referring to system 500, FIG. 6, at line 590, a low pressure sideoutlet flow (dilute solution) is shown leaving reverse osmosis unit A.This low pressure side flow from line 590 is directed through pump 591into line 592. It is then directed to joint 593 where it is split into afirst line 594 and a second line 596. The first line 594 is directedinto the high pressure side inlet feed line 595 for reverse osmosis unitE. The reverse osmosis unit E comprises a reverse osmosis memberarrangement or membrane 600 having a high pressure side 600 x and a lowpressure side 600 y. Still referring to system 500, and reverse osmosisunit E, line 596 is directed through pressure reducer 602, and intoinlet line 603 for the low pressure side of reverse osmosis unit E.

At 610, a concentrate outlet from reverse osmosis unit E is provided.The concentrate outlet 610 is directed to line 516, where it is combinedwith liquid in line 513. Thus, the reverse osmosis unit operationconducted in reverse osmosis unit A is conducted with a high pressureinlet feed comprising a combination of: original solution from line 511;low pressure side dilute solution outlet flow from reverse osmosis unitB; and, concentrate from reverse osmosis unit E. The low pressure sidefeed to reverse osmosis unit A, however, is conducted with a combinationof original solution in 511 and low pressure side dilute solution outletflow from reverse osmosis unit B.

Still referring to system 500, attention is directed to outlet line 620from reverse osmosis unit E. Outlet line 620 comprises a low pressureside outlet flow (dilute solution) from reverse osmosis unit E. It isdirected through pump 621 into line 622. Line 622 is directed to joint623 where it is split into lines 624 and 625. Line 624 is directed intohigh pressure side inlet line 626 for a high pressure side 630 x ofreverse osmosis unit F. Line 625 is directed through pressure reducer628 into low pressure inlet line 627 for a low pressure side 630 y ofreverse osmosis unit F.

Reverse osmosis unit F, then, generally comprises a reverse osmosismembrane arrangement or membrane 630 having a high pressure side 630 xand a low pressure side 630 y.

Reverse osmosis unit F is operated as a final polishing membrane fordilute solution. The operation conducted in reverse osmosis unit F isconducted with a same inlet solution (in solute concentration) directedto each side of the membrane 630, the inlet solution comprising lowpressure side outlet flow (dilute solution) from reverse osmosis unit E.At line 632 a low pressure side outlet flow for reverse osmosis unit Fis depicted, comprising a dilute solution removed from system 500 via503.

At line 635 a high pressure side concentrate line from reverse osmosisunit F is shown. This concentrate is directed to joint 636, where it iscombined with a portion of low pressure side outlet flow from reverseosmosis unit A and is directed into line 595, and into the high pressureside inlet feed to reverse osmosis unit E.

Referring to reverse osmosis unit E, then, the operation conductedtherein is conducted with a high pressure side inlet feed comprising acombination of: low pressure side outlet flow from reverse osmosis unitA; and, concentrate from reverse osmosis unit F. The low pressure sideinlet for reverse osmosis unit E comprises low pressure side outlet flowfrom for reverse osmosis unit A.

In the process in accord with system 500, as with other processesdescribed herein, each reverse osmosis membrane unit that is operatedwith both a high pressure side inlet feed and a low pressure side inletfeed, is typically either conducted with a same feed concentrationdirected to each side, or with the feed directed to each side whichdiffers in solute concentration by no more than 20%, typically no morethan 15% and usually 10% or less.

In the general terms characterized herein above, system 500 includes afirst, final, dilute solution-generating reverse osmosis unit F; first,final, concentrate solution-generating reverse osmosis unit D; and, anintermediate reverse osmosis unit system, in the example showncomprising units E, A, B, and C. In general concentrate flow is from: afirst, final, dilute solution-generating reverse osmosis unit F throughintermediate reverse osmosis membrane system (in the example shown inseries through units E, A, B and C) and then through final, concentratesolution-generating, reverse osmosis unit D. Further, for the exampleshown, low pressure side dilute solution outlet flows generally fromfirst, final, concentrate solution-generating reverse osmosis unit Dthrough the intermediate reverse osmosis unit system (comprising inseries units C, B, A and E) to first, final, dilute solution-generatingreverse osmosis unit F. The example system is operated with an originalsolution directed into the intermediate reverse osmosis unit system(comprising units E, A, B and C); in the particular system shown, intounit A.

Further, the intermediate reverse osmosis unit system (units E, A, B,and C) includes a most permeate flow-direction reverse osmosis unit (E)and a most concentrate flow-direction reverse osmosis unit (C). Inaccord with the general characterizations herein, unit B comprises anext permeate flow-direction reverse osmosis unit from unit C and asecond next concentrate flow-direction reverse osmosis unit, from unitE. Further unit A comprises a first next concentrate-direction reverseosmosis unit, from unit E; and, a second, next permeate flow-directionreverse osmosis unit, from unit C. Also, in general, units A and Bcomprise a central unit system, for the intermediate reverse osmosismembrane unit system. In general, flow feeds to the various units are ascharacterized herein above.

It is noted that in the system 500 of FIG. 6, various locations ofpumps, pressure reducers and joints are shown. Alternatives can be used,in general in accord with the principles herein. Further, it is notedthat the system of FIG. 6 can be operated with counter current flowthrough a member of the units having both inlet feed to the highpressure side and inlet feed to the low pressure side.

It is noted that in FIG. 6 a number of phantom arrowheads are indicatedby the reference “r”. These are meant to indicate that optionally undersome operating conditions, the flow in the indicated line can be in thereverse direction, i.e., in the direction identified in “r”. This willbe dependent upon operating conditions and parameters selected by theoperator of the system.

F. Another Example System, FIG. 7.

Attention is now directed to FIG. 7, in which another example system isdepicted at 700. The cascading reverse osmosis system 700 is conductedwith a plurality of reverse osmosis units, in this instance four reverseosmosis unit A-D. For the system 700, an original solution line into thesystem is depicted at 701. A concentrate out line from the system 700 isdepicted at 702 and a dilute solvent outlet from the system 700 isdepicted at 703.

According to FIG. 7, the original solution 701 is directed throughreverse osmosis pump 705 into inlet feed line 706. This liquid isdirected to joint 707 where it is split into lines 708, 709. It is notedthat prior to reaching joint 707, the inlet line 706 is modified atjoint 710, as discussed below. Line 708 is directed to the high pressureside inlet feed line 712 for reverse osmosis unit A. Line 709 isdirected through pressure reducer 713 into low pressure side inlet feedline 714, for reverse osmosis unit A.

In general, reverse osmosis unit A comprises a reverse osmosis membranearrangement or membrane 715 having a high pressure side 715 x and a lowpressure side 715 y.

At 720, a high pressure side, concentrate outlet line from reverseosmosis unit A is depicted. This concentrate is directed via line 720 tojoint 721, where the concentrate from reverse osmosis unit A is combinedwith a low pressure side outlet flow (dilute solution) from reverseosmosis unit C, as discussed below. This combination is directed intocombined line 725, to joint 726, where it is split into lines 727 and728. Line 727 is directed to a high pressure side inlet feed line 729,to reverse osmosis unit B. Line 728 is directed through pressure reducer730 to low pressure side inlet line 731 for reverse osmosis unit B.

In general, reverse osmosis unit B comprises a reverse osmosis membranearrangement or membrane 735 having a high pressure side 735 x and a lowpressure side 735 y.

From a review of reverse osmosis membrane unit B, in the system 700,FIG. 7, it can be seen that the reverse osmosis operation conducted inreverse osmosis unit B is with the same solution concentration enteringthe high pressure inlet 729 and the low pressure inlet 731, the mixturecomprising a combination of high pressure side outlet concentratesolution from reverse osmosis unit A, and as discussed below, lowpressure side outlet dilute solution from reverse osmosis unit C.

Referring still to FIG. 7, at 740 a low pressure side outlet flow(dilute solution) from reverse osmosis unit B is depicted. The solution740 from a low pressure side of osmosis unit B is directed through pump741 into line 742. The low pressure side outlet flow from reverseosmosis unit B is then directed via line 742 to joint 710 where it iscombined with the original solution feed in line 706 and, as discussedbelow, with concentrate from reverse osmosis unit D. This combination isthen directed to joint 707, to be split and used in each side of theoperation conducted in reverse osmosis unit A.

Still referring to system 700, FIG. 7, at 745 a concentrate outlet linefor reverse osmosis unit B is shown. This concentrate outlet is directedto joint 746 where it is split into lines 747 and 748. Line 747 isgenerally a high pressure side inlet feed for reverse osmosis unit C.Line 748 is directed through pressure reducer 747 into line 750, a lowpressure side inlet feed to reverse osmosis unit C.

In general, reverse osmosis unit C comprises a reverse osmosis memberarrangement or membrane 755 having a high pressure side 755 x and a lowpressure side 755 y. The reverse osmosis operation conducted in reverseosmosis unit C, is with inlet feed to each side of the reverse osmosismembrane comprising concentrate outlet flow from reverse osmosis unit B.

At 760, concentrate outlet from reverse osmosis unit C is depicted. Thisconcentrate outlet is directed through pressure reducer 761, intoconcentrate outlet line 702 for system 700.

At 765 a low pressure side outlet flow (dilute solution) from reverseosmosis unit C is provided. This low pressure side outlet from thereverse osmosis unit C is directed through pump 766 into line 767 tojoint 721. At joint 721 the low pressure side outlet from reverseosmosis unit C is combined with concentrate from reverse osmosis unit Aand is directed into joint 726, to be split and used as a feed line toopposite sides of reverse osmosis unit B.

Attention is now directed to line 770, a low pressure side outlet linefor reverse osmosis unit A. This outlet flow is directed through pump771 into pressurized line 772, which directs the low pressure sideoutlet flow (dilute solution) from reverse osmosis unit A into inletline 773 for reverse osmosis unit D.

Reverse osmosis unit D is operated as a polishing reverse osmosis unit,with no low pressure side inlet stream. The reverse osmosis unit Dcomprises a reverse osmosis membrane unit arrangement or membrane 775having a high pressure side 775 x and a low pressure side 775 y. Withinreverse osmosis unit D, feed stream 773 is the low pressure side outletfor reverse osmosis unit A. Again, there is no low pressure side inletfeed stream for reverse osmosis unit D. At 778 a permeate outlet forreverse osmosis unit D is shown. This low pressure side permeate outletline 778 directs permeate for reverse osmosis unit D out of system 700,via solvent outlet line 703.

At 780 a concentrate outlet stream is shown for reverse osmosis unit D.It is directed through pump 781 into joint 710, where it is combinedwith: pressurized low pressure side outlet flow from reverse osmosisunit B; and, pressured inlet feed from line 706, to be directed to joint707.

In general, system 700, is conducted with a plurality of reverse osmosisunits. Each reverse osmosis unit that is operated with both a highpressure inlet side feed and a low pressure inlet side feed, isconducted with the same feed concentration directed to each side of therespective reverse osmosis membrane unit. This is the case, for example,with units A, B and C. Again, polishing unit D is operated with no lowpressure side inlet feed for this particular example.

In the general language characterized above, system 700 includes: afirst, final, solvent-generating reverse osmosis unit D; a first, final,concentrate-generating reverse osmosis unit C; and, an intermediatereverse osmosis unit system in the example shown comprising units A andB. The intermediate reverse osmosis unit system (units A and B)includes: a most permeate flow-direction reverse osmosis unit A; and, amost concentrate flow-direction reverse osmosis unit B.

System 700 as depicted is conducted with:

(a) Concentrate flow from the first, final, solvent-generating reverseosmosis unit D being directed through the intermediate reverse osmosisunit system (units A and B, in the example shown in series through unitA and then unit B) into the first, final, concentrate-generating reverseosmosis unit C.

(b) Also, low pressure side (dilute solution) outlet flow from thefirst, final, reverse osmosis unit C is directed through theintermediate reverse osmosis unit system (comprising units A and B, andin the example shown in series through unit B and then unit A) to thefirst, final, solvent-generating reverse osmosis unit D.

(c) Finally, original solution is directed into the intermediate reverseosmosis unit system (comprising units A and B), in the specific exampleshown it is directed to unit A.

The various units (A, B, C and E) of unit 700 can be conducted withflows generally as characterized.

In the example system 700, FIG. 7, the only unit not operated with thesame feed to a high pressure side and a low pressure side, is unit D,which is not operated with any inlet flow to the low pressure side.

It is noted that in the system 700 of FIG. 7, each reverse osmosis unit(A, B, C) that is operated with both a high pressure side inlet feed anda low pressure side inlet feed, is depicted as conducted with a countercurrent flow. Alternatives are possible. Also, various pumps, pressurereducers and joints depicted in FIG. 7 can be alternately positioned, ifdesired.

G. Another Example System, FIG. 8

Attention is now directed to cascading reverse osmosis system 800, FIG.8. Referring to FIG. 8, cascading reverse osmosis system 800 is depictedfor processing an original solution mixture in line 801. The solutionwill be processed within the system 800 to provide a concentrate outletas indicated 802 and a solvent outlet as indicated at 803.

The cascading reverse osmosis system 800 depicted in FIG. 8, includes aplurality of reverse osmosis membrane units, in this example reverseosmosis membrane units A-D.

Referring to FIG. 8, original solution in line 801 is directed throughpump 805 to provide a solution feed in pressurized inlet line 806. Line806 is modified at joint 807 by being combined with low pressure sideoutlet flow from reverse osmosis unit B. This feed is then directed intoinlet line 808, the high pressure side inlet feed to side 810 x ofreverse osmosis unit A.

Reverse osmosis unit A comprises a reverse osmosis membrane arrangementor membrane 810 having a high pressure side 810 x and a low pressureside 810 y. Line 808 is an inlet feed line for high pressure side 810 x.For the particular system depicted, reverse osmosis unit A does not havea low pressure side inlet line.

For the particular system 800 depicted, reverse osmosis unit A isoperated with a high pressure side inlet feed, then, comprising, incombination, original solution to be processed; and, low pressure sideoutlet flow from reverse osmosis unit B.

At 812, a low pressure side outlet (dilute solution) stream from reverseosmosis unit A is depicted. This stream is directed into the solutionoutlet stream 803.

At 814, a high pressure side concentrate outlet stream from reverseosmosis unit A is depicted. It is directed into pump 815, to provide apressurized line 816, of pressurized concentrate from reverse osmosisunit A. Line 816 is directed to joint 817, where concentrate fromreverse osmosis unit A is combined with low pressure side outlet flowfor reverse osmosis unit C, the combination being directed into line818. Line 818 is directed to joint 819 where liquid carried thereby issplit into lines 820, 821. Line 820 is directed to high pressure sideinlet line 822 for reverse osmosis membrane unit B. Line 821 is directedthrough pressure reducer 823 and then into reverse osmosis low pressureside inlet line 824, for unit B.

Reverse osmosis membrane unit B generally comprises a reverse osmosismembrane arrangement or membrane 825 having a high pressure side 825 xand a low pressure side 825 y. The reverse osmosis process conducted inreverse osmosis unit B, for the cascading reverse osmosis system 800depicted, is conducted with the same liquid flow (in concentrationsolute) directed to the inlet of the high pressure side 825 x and to theinlet of the low pressure side 825 y; that liquid comprising acombination of concentrate from reverse osmosis unit A and low pressureside outlet from reverse osmosis unit C.

Still referring to system 800, FIG. 8, at 830 the low pressure sideoutlet flow is shown leaving reverse osmosis unit B and being directedthrough pump 831 to joint 807. Here, the low pressure side outlet flowfrom reverse osmosis unit B is combined with the original solution inline 806 to be directed into reverse osmosis membrane unit A.

At line 835, high pressure side concentrate is being removed fromreverse osmosis unit B. It is directed to joint 836 where it is combinedwith a dilute solution from reverse osmosis unit D and is directed vialine 837 to joint 838. At joint 838, the liquid stream from line 837 issplit, into lines 839 and 840. Line 839 is directed into the highpressure side inlet line 841 for reverse osmosis unit C. Line 840 isdirected through pressure reducer 842 into the low pressure side inletline 843 for reverse osmosis unit C.

In general, the reverse osmosis unit C includes a reverse osmosismembrane arrangement or membrane 845 having a high pressure side 845 xand a low pressure side 845 y. Line 841 directs inlet feed to highpressure side 845 x and line 843 directs inlet feed to low pressure side845 y. It is noted that the reverse osmosis operation conducted withreverse osmosis unit C is conducted with the same inlet feed (in soluteconcentration) to both the high pressure side 845 x and the low pressureside 845 y, that inlet feed comprising in combination of: low pressureside outlet flow from reverse osmosis unit D, and concentrate fromreverse osmosis unit B.

At 848, a low pressure side outlet flow line for reverse osmosis unit Cis depicted. The solution is directed through line 848 through pump 849,and then to joint 817, where it is combined with concentrate fromreverse osmosis unit A and is directed into reverse osmosis unit B forprocessing as previously described.

Line 850 is a high pressure side concentrate outlet line for reverseosmosis unit C. It is directed to joint 851 where it split into lines852 and 853. Line 852 is a high pressure side inlet line to reverseosmosis unit D. Line 853 is directed through pressure reducer 854 to lowpressure side inlet line 855 for reverse osmosis unit D.

Reverse osmosis unit D generally comprises a reverse osmosis membranearrangement or membrane 857 having a high pressure side 857 x and a lowpressure side 857 y. For the particular reverse osmosis unit D depicted,the reverse osmosis process is conducted with the same feed streams (insolute concentration) to both the upstream side via 857 x and thedownstream side 857 y of member 857.

At 858 the low pressure side outlet (dilute solution) stream for reverseoutlet unit D is depicted. It is directed through pump 859 to joint 836,where it is combined with concentrate for reverse osmosis unit B andused for the feed stream to reverse osmosis unit C.

At 860 the high pressure side concentrate is shown leaving reverseosmosis unit D. This concentrate is directed to pressure reducer 861 andthen is directed as a concentrate out in line 802, from system 800.

Referring in general to system 800 FIG. 8, it is noted that for each ofthe reverse osmosis units therein, which is conducted with both a highpressure side inlet feed and a low pressure side inlet feed, (i.e. unitsB, C and D), the inlet feed to each side of a selected unit is the same,in concentration solute. The only reverse osmosis membrane unitconducted without both high pressure side inlet and a low pressure sideinlet feed, is reverse osmosis unit A.

It is noted that for the system 800 of FIG. 8, those reverse osmosisunits (B,C, D) operate with both a high pressure side inlet feed and alow pressure side inlet feed, are depicted as conducted with countercurrent flow. Alternatives are possible.

In addition, the system 800 of FIG. 8, is depicted with various pumps,pressure reducers, and joints. Alternative positions or configurationsof these are possible.

In general terms characterized above, system 800 can be viewed asincluding: a first, final, solvent (or dilute solution)—generatingreverse osmosis unit A; a first, final concentrate-generating reverseosmosis unit D; and, an intermediate reverse osmosis unit membranesystem comprising units B and C. Unit B can be considered a mostpermeate flow-direction reverse osmosis unit, of the intermediatesystem; and, unit C can be viewed as comprising a most concentrateflow-direction reverse osmosis unit, of the intermediate system.

Further, in general, operation of the system 800 can be characterized asfollows:

(a) Concentrate flow from the first, final, solvent (or dilutesolution)-generating reverse osmosis unit A is directed through theintermediate system (in the example shown in series through units B andC) to the first, final, concentrate-generating reverse osmosis unit D.

(b) Low pressure side outlet flow (dilute solution) from the first,final, concentrate-generating reverse osmosis unit D can be viewed asdirected through the intermediate system (in the example shown in seriesthough units C and B) into the first, final solvent (or dilutesolution)—generating reverse osmosis unit A.

(c) Further, in the example depicted, the original solution can beviewed as directed into the first, final, solvent (or dilutesolution)—generating reverse osmosis unit A.

Of course principles analogous with FIG. 8 could be applied, with theoriginal solution directed into first, final, concentrate-generatingreverse osmosis unit D, with the systems appropriately modified for theintended flows.

The particular system of FIG. 8, is configured for a situation in whichthe concentrate out 802, is desired to be substantially higher inconcentration than the concentration of the feed solution , 801 and thefeed solution 801 is relatively dilute such that solvent can beextracted in a single step reverse osmosis process of reverse osmosisunit A.

H. Examples of Modified Versions of FIG. 8-FIGS. 9, 9A and 10

As discussed above, the various equipment systems characterized herein,can be modified with respect to: pump location, pressure reducerlocation; and, joints, to accomplish different effects and thus providefor different processes. FIGS. 9, 9A and 10 provide examples relating tomodification of the four reverse osmosis unit system 800, FIG. 8.

Referring to FIG. 9, system 900 generally involves the use of fourreverse osmosis units A, B, C and D. Reverse osmosis unit A is aconventional reverse osmosis unit, and does not include a low pressureside inlet. Rather reverse osmosis unit A has a high pressure side inlet901, a high pressure side (concentrate), outlet 902 and a low pressureside outlet 903 which, for system 900 comprises a purified solventoutlet 904.

Reverse osmosis unit B is a most permeate flow-direction reverse osmosisunit, in the intermediate reverse osmosis unit system comprising units Band C. Reverse osmosis unit B has a reverse osmosis membrane arrangementor membrane 910 with a high pressure side 911 and a low pressure side912. Reverse osmosis unit B includes a high pressure side inlet 913 anda low pressure side inlet 914, a high pressure side, concentrate outlet915 and a low pressure side, outlet 916.

Reverse osmosis unit C comprises a most concentrate flow-directionreverse osmosis unit in the intermediate reverse osmosis unit systemcomprising units B and C. Reverse osmosis unit C comprises a reverseosmosis membrane arrangement or membrane 920 having a high pressure side921 and a low pressure side 922. Unit C has a high pressure side inlet923, a low pressure side inlet 924, high pressure side, concentrate,outlet 925 and a low pressure side, dilute solvent solution outlet 926.

Reverse osmosis unit D is a final, concentrate-generating reverseosmosis unit for system 900. Reverse osmosis unit D comprises a reverseosmosis membrane arrangement or membrane 930 having a high pressure side931 and a low pressure side 932. Unit D includes a high pressure sideinlet 933, a low pressure side inlet 934; a high pressure side,concentrate, outlet 935; and, a low pressure side, dilute solutionoutlet 936.

For system 900, at 940 original solution inlet is shown. At 941,concentrate outlet is shown. Various pumps are indicated in this systemat 942 with various pressure reducers are indicated in the system at943.

Referring to FIG. 9, it can be seen that the system is operated withoriginal solution 940 directed through pump 942 into inlet 901 forreverse osmosis unit A. At inlet 901, solution 940 is mixed with lowpressure side outlet 916 from reverse osmosis unit B. At reverse osmosisunit A, a reverse osmosis operation is conducted providing a lowpressure side outlet flow 903 which leaves system 900 as solvent outlet904. High pressure side outlet (concentrate) is shown leaving reverseosmosis unit A and being directed into joint 905 where it splits intolines 906 and 907. Line 907 is directed through pressure reducer 943 andinto the low pressure side 912 of reverse osmosis unit B via 914. Line906 is directed to joint 908 where it combines with flow from 926 tofeed inlet 913 to the high pressure side 911 of reverse osmosis unit B.The reverse osmosis operation conducted in reverse osmosis unit B, iswith high pressure side inlet 913 comprised of solution from lowpressure side outlet 926 from reverse osmosis unit C and high pressureside concentrate solution from high pressure side outlet 902 fromreverse osmosis unit A. It is noted reverse osmosis unit B is set up forcounter current flow, although alternatives are possible.

From reverse osmosis unit B, low pressure side outlet 916 is showndirected into inlet 901 for reverse osmosis unit A, as previouslydescribed. Concentrate in line 915 from reverse osmosis unit B is usedas low pressure side inlet for reverse osmosis unit C and is alsocombined with dilute solution low pressure side outlet flow from reverseosmosis unit D in 936 at joint 918 to serve as inlet feed 923 to thehigh pressure side of reverse osmosis unit C. Reverse osmosis unit C isoperated with counter current flow and a high pressure side inlet flowat 923 comprising a combined flow solution of low pressure side outletfrom reverse osmosis unit D and high pressure side outlet from reverseosmosis unit B. (At 919, line 915 is split to provide low pressure sideinlet flow 924, for unit C).

Low pressure side outlet from reverse osmosis unit D, is shown at line936 and is used as a portion of the high pressure side inlet for reverseosmosis unit C. High pressure side outlet 925 from reverse osmosis unitC is split at joint 946, and is used as both the high pressure sideinlet 933 and low pressure side inlet 934 for reverse osmosis unit D.The concentrate outlet from reverse osmosis unit D, at 935, generallycomprises the concentrate outlet from the system 900, once reduced inpressure. The low pressure side outlet 936 from reverse osmosis unit Dis combined with flow in line 917 at joint 918 and used as a highpressure side inlet at 923 for reverse osmosis unit C.

From a review of FIG. 9, it can be understood that each of reverseosmosis units B, C and D are operated with: a high pressure side inletflow; a low pressure side inlet flow; and, each is operated with acounter current flow. Of course, an alternative to counter current flowis possible.

The system of FIG. 9 can be generally characterized as involving afirst, final, solvent (or dilute solution)—generating unit A; a first,final, concentrate—generating unit D, and an intermediate reverseosmosis unit system comprising two units, units B and C; unit B being amost permeate flow-direction unit and unit C being a most concentrateflow-direction unit. The system of FIG. 9 will be particularlyadvantageous, if the system inlet feed solution 940 is dilute enoughsuch that solvent can be extracted in a single step reverse osmosisprocess in reverse osmosis unit A and, higher concentrate solution isdesired such as could be produced via the high pressure side outlet ofreverse osmosis unit D at 935.

Any number of intermediate units could be used to obtain progressivelyhigher solution concentrations.

Note that FIG. 9 is similar to FIG. 8, other than the location of flowjoints. As stated previously, various configurations of flow joints,pumps, and pressure reducing devices are possible. Several examples arepresented herein, however, these examples are not intended to, nor dothey, represent all of the various possible configurations of thecascading reverse osmosis system claimed herein.

It is noted that in FIG. 9 a number of phantom line arrowheads aredesignated by “r”. These are intended to indicate that optionally theflow in the line indicated can be in the reverse direction from thatdiscussed above, i.e., the direction of arrowhead “r”. This will be amatter selected by the operator of the system, based upon parameters foroperation selected.

In FIG. 9A, a variation in system 900, is depicted 1960. The system 1960comprises four reverse osmosis units A, B, C, and D.

Original solution flow into system 1960 is shown at 1961. It is directedthrough pump 1962 into inlet feed line 1963 for a high pressure side ofunit D; unit D comprising a membrane or membrane arrangement 1964 havinga high pressure side 1964 x and a low pressure side 1964 y. Concentrateoutlet flow from unit D is shown at line 1965 directed through pressurereducer 1966 to provide a final concentrate outlet 1967. Low pressureside outlet flow from unit D is shown at line 1969 directed through pump1970 into high pressure side inlet line 1971 for unit C. Unit Cgenerally comprises reverse osmosis membrane or membrane arrangement1973 having an upstream side 1973 x and a downstream side 1973 y. Thehigh pressure side, concentrate, outlet from unit C is shown at 1975,directed through pressure reducer 1976 to provide a low pressure sideinlet feed 1977 for reverse osmosis unit D.

At 1980, a low pressure side inlet line from unit C is shown directedthrough pump 1981 into high pressure side inlet feed 1982 for reverseosmosis unit B. Reverse osmosis unit B comprises a membrane arrangementor membrane 1983 having a high pressure side 1983 x, and a low pressure,downstream, side 1983 y. High pressure, concentrate, outlet from unit Bis shown at line 984 directed through pressure reducer 1985 into lowpressure side inlet feed 1986, for reverse osmosis unit C. At 1987, alow pressure side outlet from unit B is shown directed through pump 1988into inlet feed 1989 for high pressure side of unit A. Unit A includes amembrane 1990 having a high pressure side 1990 x, and a downstream, lowpressure side 1990 y. At 1991, a low pressure side outlet flow from unitA is shown, providing a dilute solution outlet from system 1960. At1982, a high pressure side outlet from unit A is shown directed throughpump 1983 and pressure reduction 1984 to provide an inlet line 1985 forunit B.

Of course, variations and specific pump pressure reducer locations canbe provided, in the system in accord with FIG. 9A.

FIG. 9A demonstrates the principle of isolating one or more flows, andnot providing complete cascading flow, within the system. For example,since the high pressure side inlet feed 971 to unit C comes from unit D,the high pressure side outlet feed from unit C is back into unit D; and,dilute solution flow from unit C is directed into unit B as highpressure flow, and concentrate flow from line 984 from unit B isdirected back into unit C.

Stated in more general terms, first reverse osmosis membrane unit (D) isoperated with both a high pressure side inlet feed and a low pressureside inlet feed, the high pressure side inlet feed being originalsolution flow. Low pressure side inlet feed is pressure side concentrateoutlet flow from a second unit (C). For the system 1960, a low pressureside outlet flow from the first unit (D) is directed into the secondunit, and not elsewhere. The high pressure side concentrate outlet flowfrom the second unit (C) is directed into the first unit (D) and notelsewhere. This provides a closed loop for concentrate in high pressure,side of unit C, and the low pressure side of unit D. At least a thirdunit (B) provided, receiving low pressure side outlet flow from thesecond unit (C).

A system similar to unit 9A can be used when it is desirable to changethe specific solute the system. For example, assume that the inlet flowat 1961 comprises a particularly caustic material, for reverse osmosismembrane. Then, the first membrane unit D would be constructed,typically more expensively, to manage the material. However, fordownstream side of unit C through units B and A, the system could becharged with a different (less caustic) solute, to facilitate operationwith ordinary, not high resistance, membranes from units A, B and C.

In general, a system in accord with FIG. 9A will be referred to as aclosed loop system in that it prevents movement of a single (solute)concentrate completely through the system, if desired.

Of course, in the system of FIG. 9A there is also no specificrequirement that the same total solvent composition be used in each ofthe isolated loops, although solvent will move across the membranes inoperation.

In FIG. 10, system 950 is depicted also comprising four reverse osmosisunits A, B, C and D. Reverse osmosis unit A comprises a reverse osmosismembrane arrangement or membrane 951 having a high pressure side 952 anda low pressure side 953. Unit A includes a high pressure side inlet 954,but no low pressure side inlet. A high pressure side (concentrate)outlet flow is shown at 955. The low pressure side outlet flow is shownat 956 and comprises the solvent outlet from the system 950.

Reverse osmosis unit B comprises a reverse osmosis membrane arrangementor membrane 957 having a high pressure side 958 and a low pressure side959. High pressure side inlet 960 comprises a high pressure side(concentrate) outlet 955 from unit A. Unit B includes a low pressureside inlet 961, configured for counter current flow in unit B, withrespect to the inlet flow 960 to the high pressure side.

Low pressure side outlet 962 from unit B, is directed to high pressureside inlet 954 of unit A. High pressure side outlet (concentrate) fromunit B, is shown at 963.

Unit C comprises a reverse osmosis membrane arrangement or membrane 965having a high pressure side 966 and a low pressure side 967. Highpressure side inlet 968 is shown. The high pressure side outlet(concentrate) is shown at 969. A low pressure side outlet (dilutesolution) is shown at 970. A low pressure side inlet is shown at 971.Unit C is shown here as configured for counter current flow.

Unit D comprises a final, concentrate-generating reverse osmosis unitthat includes a reverse osmosis membrane arrangement or membrane 975having a high pressure side 976 and a low pressure side 977. Unit Dincludes a high pressure side inlet 978, and a high pressure side outlet(concentrate) 979. The high pressure side concentrate outlet 979provides for final concentrate removal 980 from system 950. Unit Dincludes a low pressure side inlet 981 configured for counter currentflow within unit D. The low pressure side outlet is shown at 982, fromreverse osmosis unit D.

Original solution inlet to system 950 is shown at 985.

From a review of FIG. 10, it will be understood that the system includesa plurality of reverse osmosis unit pumps 986 and pressure reducers 987appropriately positioned for operation.

Still referring to FIG. 10, the system 950 is operated in general, withoriginal solution 985 directed into reverse osmosis unit At highpressure side inlet 954, where it is combined with low pressure sideoutlet 962 from reverse osmosis unit B which has been pressurized.Reverse osmosis unit A is not conducted with a low pressure side inlet,and comprises a first, final, solvent-generating reverse osmosis unit Aat the most solvent end of the system. Solvent is shown removed from thesystem at 956. High pressure side outlet (concentrate) is shown at line955 being directed to unit B as a high pressure side concentrate inlet960. Low pressure side inlet 961 for reverse osmosis unit B compriseslow pressure side outlet 970 from reverse osmosis unit C. Concentratefrom reverse osmosis unit B at line 963 is shown directed into reverseosmosis unit C a high pressure side inlet 968. High pressure side,concentrate, outlet from reverse osmosis unit C is shown at 969 directedto joint 990, where it is split to provide both high pressure side inletfeed 978 and low pressure side inlet feed 981 to reverse osmosis unit D.Low pressure side outlet 982 from reverse osmosis unit D is shown usedas the low pressure side inlet 971 for reverse osmosis unit C.

Still referring to FIG. 10, system 950 can be viewed as comprising: afinal solvent-generating reverse osmosis unit A; intermediate reverseosmosis unit system comprising units B and C, and a mostconcentrate-generating reverse unit D. Further, the intermediate reverseosmosis unit system can be characterized as comprising a most permeateflow-direction unit B and a most concentrate direction unit C.

It should be noted that various ones of pumps are optional and notrequired for system operation. Also it is noted that various ones ofpressure reducers 987 are optional and not required for systemoperation.

The present invention can be used in conjunction various levels of preand post treatment including, but not limited to, filtration, ortreatment with activated carbon or other selective absorbents, partialdistillation, etc.

The present invention can be used in conjunction with various ballast,surge, or storage tanks in between the various membrane stages.

IV. Some Additional Example Systems, FIGS. 11-13

The figures thus far described were included in the disclosure of U.S.provisional 61/131,947, filed Jun. 13, 2008. In this section, FIGS.11-13, which include some features not previously described, aredepicted. These arrangements can provide an understanding of someadvantageous applications of the principles described herein.

A. A First Additional Example System and Process, FIG. 11.

Attention is now directed to FIG. 11, in which an additional examplesystem is depicted at 2000. The cascading reverse osmosis system 2000 isconducted with a plurality of reverse osmosis units, in this instancefive reverse osmosis units A-E. For the system 2000, an originalsolution flow line into the system is depicted at 2001. A concentrateoutlet line from the system 2000 is depicted at 2002, and a purifiedsolvent outlet line from the system 2000 is depicted at 2003.

According to FIG. 11, the original solution 2001 is directed throughreverse osmosis pump 2005, into feed line 2006. The liquid is thendirected to low pressure side inlet line 2012 for reverse osmosis unitA. In general, reverse osmosis unit A comprises reverse osmosis membranearrangement or membrane 2015 defining a high pressure side 2015 x and alow pressure side 2015 y. In the general terms, used herein, the reverseosmosis unit A of system 2000 is a first, final, concentrateoutlet-generating reverse osmosis unit.

From reverse osmosis unit A, the low pressure side outlet solution(reduced-solute solvent) out is indicated at 2020. This line is directedto low pressure side inlet line 2029, of reverse osmosis unit B. Reverseosmosis unit B comprises reverse osmosis membrane arrangement ormembrane 2030 defining a high pressure side 2030 x and a low pressureside 2030 y. A low pressure side solution (reduced-solute solvent)outlet is shown at 2040. This outlet directs low pressure side outletflow into low pressure side inlet line 2041 for reverse osmosis unit C.In general terms used herein, reverse osmosis unit B is a member of anintermediate reverse osmosis membrane unit system comprising at leastone reverse osmosis unit. In the particular system 2000 depicted in FIG.11, the intermediate reverse osmosis membrane unit system comprisesmultiple reverse osmosis units, and, in particular the system 2000depicted, it comprises three units B, C and D.

In general, reverse osmosis unit C comprises a reverse osmosis membranearrangement or membrane 2045, defining a high pressure side 2045 x and alow pressure side 2045 y.

At 2046, a low pressure side outlet (reduced-solute solvent) flow fromreverse osmosis unit C is depicted. Line 2046 directs the low pressureside outlet from reverse osmosis unit C into low pressure side inletline 2048 for reverse osmosis unit D.

In general, reverse osmosis unit D comprises reverse osmosis membranearrangement or membrane 2050 defining a high pressure side 2050 x and alow pressure side 2050 y. At 2051, a low pressure side outlet(reduced-solute solvent) is depicted, directing low pressure side outletflow: from reverse osmosis unit D into line 2052; through reverseosmosis unit pump 2053; and, into a high pressure side inlet line 2055for reverse osmosis unit E.

In general terms, reverse osmosis unit E comprises a reverse osmosismembrane arrangement or membrane 2060 defining a high pressure side 2060x and a low pressure side 2060 y. At 2061, a low pressure side outletline for reverse osmosis unit E is depicted. Line 2061 provides forreduced-solute solvent outflow to the purified solvent out line 2003 forthe system 2000. In the general terms used herein, reverse osmosis unitE is a first, final, solvent outlet-generating reverse osmosis unit.Reverse osmosis unit A is a first, final, concentrate outlet-generatingreverse unit. Reverse osmosis unit D is a most permeate flow-directionreverse osmosis unit in the intermediate reverse osmosis membrane unitsystem; reverse osmosis unit B is a most concentrate flow-directionreverse osmosis unit, in the intermediate reverse osmosis unit membraneunit system; and, reverse osmosis unit C is a central unit in theintermediate reverse osmosis unit system.

At 2062, a high pressure side (concentrate) outlet line for reverseosmosis unit E is depicted. That is, the outlet concentrate from reverseosmosis unit E is directed into line 2062. It is then directed throughpressure reduction device 2063 into line 2064, by which it is directedinto a high pressure side inlet line 2065, for reverse osmosis unit D,and thus into the intermediate reverse osmosis unit system comprisingunits B, C and D. At 2066, a concentrate outlet line is shown fromreverse osmosis unit D. This concentrate is directed through reverseosmosis pump 2068, into line 2069 and eventually to high pressure sideinlet line 2070, for reverse osmosis unit C.

From reverse osmosis unit C, a high pressure side outlet line is shownat 2071. This would receive the concentrate from reverse osmosis unit C,and direct it through reverse osmosis pump 2072, from which it isdirected into a high pressure side inlet line 2073 for reverse osmosisunit B. Concentrate from reverse osmosis unit B is shown directed into ahigh pressure side concentrate outlet line 2074, by which concentrateleaves reverse osmosis unit B, and thus the intermediate reverse osmosisunit system comprising units B, C and D. Line 2074 is directed throughreverse osmosis unit pump 2075 into line 2076, and eventually into highpressure side inlet line 2077 for reverse osmosis unit A. Concentrateout from reverse osmosis unit A is directed into a concentrate outflowline 2078, eventually being directed through a pressure reducer 2079,and into concentrate outlet flow line 2002.

The configuration of FIG. 11 can be used to take advantage of someenergy savings. In particular, it is noted that in use of reverseosmosis unit systems in accord with the present disclosure, the amountof pressure needed for a reverse osmosis process generally goes up, asthe volume of liquid goes down and solute concentration increases. Thatis, in the more concentrated high pressure side concentrate inlet flows,relatively high pressures are needed for the reverse osmosis operation.Thus, referring to FIG. 11, the operating pressure differential acrossreverse osmosis unit D is, for typical operation, lower than thepressure differential across reverse osmosis unit A. Indeed, it isanticipated that for a typical system, the pressure differential acrossthe reverse osmosis unit D could be about 50 psi, with the pressureacross the remaining units in concentrate flow direction, i.e. units C,B and A, respectively, increasing. For example, reverse osmosis unit Cmight be operated at 200 psi differential, unit B at 400 psidifferential, and unit A at a 690 psi differential.

The system of FIG. 11 is configured so that there is no step-downbetween reverse osmosis units A, B, C and D to save energy. Further, asthe concentrate moves from unit D through C through B to A, pressure isincreased as concentration solute increases, with each system takingadvantage of the pressure increase previously put in, for example at2068 and 2072.

It is noted that the principles described with respect to the system ofFIG. 11 can be applied in a variety of alternately configured systems,and with an alternate number of reverse osmosis units. In general, acharacteristic of FIG. 11, is that with respect to each reverse osmosisunit that is operated with each of: a high pressure side inlet; a highpressure (concentrate) side outlet, a low pressure side inlet and a lowpressure side outlet, i.e. reverse osmosis units A, B, C and D, betweeneach pair of such units is located a reverse osmosis pump (or step ofincreasing pressure) in the concentrate flow direction; and, betweeneach pair of such units there is located no pressure reduction step-downin the permeate flow direction. It is also noted that in the specificexample system of FIG. 11, there is no pump located in the low pressureside outlet flow line from any of units (A, B, C) which has both a highpressure side concentrate inlet and a low pressure side inlet, as wellas a high pressure side outlet and a low pressure side outlet.Optionally, pumps could be provided at those locations.

In general terms, the system of FIG. 11 can be characterized asincluding an intermediate reverse osmosis unit system (units B, C and D)which has no pressure reducer or step-down unit therein, i.e. between antwo units (B, C, D) therein, and in which there is no pump in thepermeate or low pressure side outlet flow line between any two units (B,C, D) therein.

For the example system of FIG. 11, the only pressuring-reducingstep-downs are the ones identified at 2079 and 2063; the one at 2079being the final concentrate outlet pressure-reducing step-down; and, theone at 2063 adjusting pressure from the operation of final,solvent-generating reverse osmosis unit E to the proper inlet pressurefor line 2065; i.e. inlet pressure for concentrate (the high pressureside) inlet feed for the intermediate reverse osmosis unit system. Bothof these pressure reducing devices can be optional, as well as pumps2068, 2072 and 2075.

It is also noted that reverse osmosis unit E is not operated with apermeate side inlet. Rather, it is final solvent purification reverseosmosis unit, analogous to ones previously described herein.

Again, it is noted that the system of FIG. 11 as described, isconfigured for a relatively efficient energy use. In particular, energyuse in a reverse osmosis system will be a function of pressuredifferential and volume. As concentrate moves toward a more and moreconcentrated status, the liquid volume decreases and higher pressure isgenerally needed to produce sufficient gains in solute concentration ateach step in the process. The system of FIG. 11 is configured forefficient use of the energy put in by the various pumps, by not havingstep-down occurring in as frequent locations as certain previouslydescribed systems.

It is noted that the principles described in connection with FIG. 11,can be configured in alternate systems with alternate numbers of reverseosmosis units, alternation and original solution in location, and/oralternate locations of equipment.

It is also noted that each and every step in equipment configurationdepicted in FIG. 11 is not required, in order to obtain some benefit inaccord with the principles thereof.

B. The System and Process of FIG. 12

Yet another variation in the principles described herein, is depicted inconnection with the process and system of FIG. 12. Referring to FIG. 12,reverse osmosis system 3000 is depicted. At 3001, original solution inis depicted. Concentrate outflow from the system 3000 is depicted at3002, and purified solvent outflow is depicted at 3003.

The particular system 3000 depicted comprises reverse osmosis units A,B, C, D and E. In terms used herein, reverse osmosis unit A is a first,final, concentrate outlet-generating reverse osmosis unit; reverseosmosis unit E is a first, final, solvent or purified solventoutlet-generating reverse osmosis unit; and, reverse osmosis units B, C,D form an intermediate reverse osmosis unit system; with unit Bcomprising a final concentrate-flow-direction unit therein; reverseosmosis unit D comprising a final, solute-reduced solvent or permeateflow-direction reverse osmosis unit of the intermediate reverse osmosisunit system; and with reverse osmosis unit C comprising a central unitof the intermediate reverse osmosis unit system.

In particular, and still referring to FIG. 12, solution in at line 3001is shown directed through reverse osmosis pump 3005 and into line 3006,whereby it is directed into low pressure side inlet flow line 3010 forreverse osmosis unit A.

Reverse osmosis unit A comprises reverse osmosis membrane arrangement ormembrane 3015 defining a high pressure side 3015 x and a low pressureside 3015 y. For reverse osmosis unit A, a low pressure side outlet line3020 is shown directing low pressure side outlet flow to joint 3021. Atjoint 3021, the low pressure side outlet flow from reverse osmosis unitA is split into lines 3022 and 3023. Line 3022 is shown directed to lowpressure side inlet line 3029 for reverse osmosis unit B.

In general, reverse osmosis unit B comprises reverse osmosis membranearrangement or membrane 3030 defining a high pressure side 3030 x and alow pressure side 3030 y. At 3040, a low pressure side outlet forreverse osmosis unit B is shown directed to joint 3041, where it issplit into lines 3042 and 3043. Line 3042 is directed to low pressureinlet line 3034 for reverse osmosis unit C.

In general, reverse osmosis unit C comprises a reverse osmosis membranearrangement or membrane 3045 defining a high pressure side 3045 x and alow pressure side 3045 y. At 3046, low pressure side outlet line forreverse osmosis unit C is depicted, directing low pressure side outletflow from unit reverse osmosis unit C to joint 3047, where the flow issplit into lines 3048 and 3049.

Low pressure side flow in line 3048 is directed to low pressure sideinlet line 3050 for reverse osmosis unit D. In general, reverse osmosisunit D comprises a reverse osmosis membrane arrangement or membrane 3051defining a high pressure side 3051 x and a low pressure side 3051 y. Alow pressure side outlet flow from reverse osmosis unit D is shown in3052 directed to reverse osmosis pump 3053 and into high pressure sideinlet line 3054 for reverse osmosis unit E.

Reverse osmosis unit E generally comprises a reverse osmosis membranearrangement or membrane 3055 defining a high pressure side 3055 x and alow pressure side 3055 y. Low pressure side solution outlet flow forreverse osmosis unit E is shown at line 3003, comprising permeate orsolvent outlet flow from the system 3000. At 3056, a high pressure sideconcentrate outlet flow for reverse osmosis unit E is depicted, directedinto pressure reduction unit 3057, to be directed via line 3058 intohigh pressure side inlet line 3059 for reverse osmosis unit D. At 3060,a high pressure side concentrate outlet flow from reverse osmosis unit Dis shown, directed to joint 3061, where it is combined with flow fromline 3049 (after flow from line 3049 has been pressurized at pump 3062)and is directed into line 3063 from joint 3061. The combined flow, inline 3063 is directed to a high pressure side concentrate inlet line3066, for reverse osmosis unit C.

At 3067, a high pressure side concentrate outlet for reverse osmosisunit C is shown directed to joint 3068, where it is combined with flowin line 3069, and is directed into line 3070. Flow into line 3069comprises the flow from line 3043 after being directed through, andpressured by, reverse osmosis unit pump 3071. Concentrate in pressurizedline 3070 is directed to high pressure side inlet line 3072, for reverseosmosis unit B.

At 3075, a high pressure side, concentrate, outlet flow for reverseosmosis unit B is depicted, directed to joint 3076, where it is combinedwith flow from line 3077 and directed into line 3078. Flow in line 3077,comprises the flow from line 3023 after having been pressurized bypassage through reverse osmosis pump 3079. High pressure sideconcentrate outlet flow at line 3078 from joint 3076 is directed throughpump 3080, into high pressure side concentrate inlet line 3081, forreverse osmosis unit A.

At 3082, high pressure side concentrate outlet from reverse osmosis unitA is shown being directed to pressure reducer or pressure step-down unit3035, and ultimately to concentrate outlet line 3002.

It is noted that particular system depicted FIG. 12 is operated withmultiple, in this example four reverse osmosis units A, B, C and D, eachof which has: a high pressure side concentrate inlet; a high pressureside concentrate outlet; a low pressure side inlet; and, a low pressureside outlet. Between each of these four units is provided a joint whichdirects a portion of reduced-solute, solvent, outflow from a next orprevious upstream unit (in permeate or low pressure side outlet flowdirection) into two streams. A first stream is directed into the lowpressure side inlet of the next downstream unit (in permeate or lowpressure side outflow direction); and, a second stream that is directedthrough a pump and is then combined with a high pressure sideconcentrate outlet flow from that same next permeate flow-directiondownstream unit (or, alternately stated, the next upstream concentratedirection unit).

It is noted that the final reverse osmosis unit E is not conducted witha low pressure side inlet, but rather comprises a final solventpurification reverse osmosis unit in the system.

In general, the configuration of FIG. 12 can be modified with respect tosuch features as the specific flow line and pump configurations andspecific number of reverse osmosis units. Pressure reducing devices 3035and 3057 are optional. In addition, pump 3080, and any of the individualbypass lines and associated pumps, are optional.

This system depicts how a process analogous to that conducted withrespect to FIG. 11 can be further modified for energy efficiency. Inparticular, as material moves in the permeate flow-direction (lowpressure side flow direction) from unit A, to unit B, to unit C, to unitD, the volume in the low pressure side outlet flow increases, as aresult of the solvent addition coming from the reverse osmosis process;i.e. solvent passage across the various reverse osmosis membranes in thereverse osmosis membrane units. At each downstream joint, at least aportion of the increase in volume is taken back out, is re-pressurizedand is put in the concentrate outlet flow form in the next permeateflow-direction (low pressure side flow direction) downstream unit; thiscould alternately be identified as the next upstream unit in concentrateflow-direction. This reduces the amount of energy needed to accomplishthe downstream reverse osmosis operations (in the permeate direction)with respect to an increasing volume of solution. Another way to statethis, is that a certain amount of solution is bypassed back between anytwo of the reverse osmosis units A, B, C and D.

Thus, referring back to the process of previously discussed FIG. 11, andreverse osmosis unit D, there was a high volume of liquid passingthrough the system, but the differential pressure for operation of areverse osmosis step for that membrane unit (D) was relatively low, withstep wise increases in pressure as volume decreased in the concentrateflow direction. With respect to the system of FIG. 12, each reverseosmosis unit is operated with a relatively high differential pressure;and a high solvent volume is not pushed through the entire system, butrather is bypassed back. Thus, in the process of FIG. 12 energyadvantage is obtained by not pressurizing a higher volume of liquid thanneeded, at various ones of the reverse osmosis units. As one can see, itis possible to mix and match various configurations from the process ofFIG. 12 with the process of FIG. 11.

C. The Reverse Osmosis Process and System of FIG. 13

In FIG. 13, another reverse osmosis system is depicted generally at4000. The reverse osmosis system 4000 is a modification of the system3000, FIG. 12. In particular, the system 4000 uses reverse osmosis unitsA, B, C, D and E somewhat analogously to the use of analogouslyidentified reverse osmosis units in FIGS. 11 and 12. However, in FIG.13, some additional smaller units F, G and H are used, one each betweenunits A, B, C, and D, respectively. The operation of these units (FIG.14) will be understood from the following general description of system4000.

Before returning to a detailed description of system 4000, FIG. 13, thegeneral terms used herein, the following characterizes the system 4000:reverse osmosis unit A is a first, final, concentrate-direction reverseosmosis unit; reverse osmosis unit E is a first, final, permeate orreduced solute solvent-direction reverse osmosis unit; reverse osmosisunits F, B, G, C, H and D form an intermediate reverse osmosis unitsystem; reverse osmosis unit F is a final concentrate flow-directionreverse osmosis unit in the intermediate reverse osmosis unit system;and, reverse osmosis unit D is a final reduced-solute solvent orpermeate flow-direction reverse osmosis unit, in the intermediatereverse osmosis unit system. Thus, units B, G, C and H are central unitsin the intermediate reverse osmosis unit system.

Referring to FIG. 13, at 4001 original solution flow into the system isdepicted at 4001. Concentrate outflow from the system is depicted atline 4002, and (purified) solvent outflow is depicted at 4003. Solutioninflow at 4001 is shown directed through reverse osmosis pump 4005 andinto line 4006, from which it is directed into low pressure side inletline 4012 for reverse osmosis unit A. Reverse osmosis unit A generallycomprises a reverse osmosis membrane arrangement or membrane 4015defining a high pressure side 4015 x and a low pressure side 4015 y. Lowpressure side outlet flow from reverse osmosis unit A is shown at line4020, directed to joint 4021. At joint 4021 it is split into lines 4022and 4023. Line 4022 generally comprises a low pressure side inlet flowto reverse osmosis unit F, which comprises a reverse osmosis membrane5000 defining a high pressure side 5000 x and a low pressure side 5000y. For reverse osmosis unit F, a low pressure side outlet flow is shownat line 4029 directed as low pressure side inlet flow to reverse osmosisunit B.

Reverse osmosis unit B generally comprises reverse osmosis unit membranearrangement or membrane 4030 defining a high pressure side 4030 x and alow pressure side 4030 y. At 4040, a low pressure side outlet line fromreverse osmosis unit B is shown directed to joint 4041 where it splitinto lines 4042 and 4043. Line 4042 is a low pressure side inlet line toreverse osmosis unit G. Reverse osmosis unit G generally comprises areverse osmosis membrane arrangement or membrane 5010 defining a highpressure side 5010 x and a low pressure side 5010 y.

At 4044, low pressure side outlet flow from reverse osmosis unit G isshown directed as a low pressure inlet flow to reverse osmosis unit C.Reverse osmosis unit C generally comprises a reverse osmosis membranearrangement or membrane 4045 defining a high pressure side 4045 x and alow pressure side 4045 y. At 4046, low pressure side outlet flow fromreverse osmosis unit C is shown directed to joint 4047, where it issplit into line 4048 and line 4049. Line 4048 is directed as a lowpressure side inlet flow into reverse osmosis unit H, which generallycomprises reverse osmosis membrane arrangement or membrane 5020 defininga high pressure side 5020 x and a low pressure side 5020 y.

At line 4050, a low pressure side outlet flow from reverse osmosis unitH is shown directed into a low pressure side inlet flow for reverseosmosis unit D. Reverse osmosis unit D generally comprises reverseosmosis membrane arrangement or membrane 4051 defining a high pressureside 4051 x and a low pressure side 4051 y.

At line 4052, low pressure side outlet from reverse osmosis unit D isshown directed through reverse osmosis pump 4053 into line 4054, a highpressure side inlet line for reverse osmosis unit E.

Reverse osmosis unit E generally comprises a reverse osmosis membranearrangement or membrane 4055 defining a high pressure side 4055 x and alow pressure side 4055 y.

Line 4003, the permeate outlet line from the system 4000, is a lowpressure side outlet line from reverse osmosis unit E.

At 4056, a high pressure side concentrate outlet line from reverseosmosis unit E is shown directed through pressure reduction or pressurestep-down unit 4057 and into line 4058 by which it is directed to highpressure side inlet line 4059 for reverse osmosis unit D. At 4060, ahigh pressure side concentrate outlet from reverse osmosis unit D isdirected to joint 4061, where it joined with liquid in line 4063, whichwould generally comprise liquid from line 4049 after having beenpressurized at pump 4062. This combined flow at line 4065 is directed asa high pressure side inlet flow to reverse osmosis unit H.

At 4066, a high pressure side concentrate outlet flow from reverseosmosis unit H is directed into high pressure side inlet flow line 4067for reverse osmosis unit C.

At 4068, a high pressure side concentrate outlet from reverse osmosisunit C is shown directed to joint 4069, where it is combined with liquidin line 4070. Liquid in line 4070 comprises the liquid from line 4043after being directed through reverse osmosis pump 4071. The combinedline from joint 4069 is shown directed at line 4072 as the high pressureside concentrate inlet flow line to reverse osmosis unit G.

At 4075, high pressure side concentrate outlet flow from reverse osmosisunit G is shown, directed thereby to high pressure side inlet line 4076for reverse osmosis unit B.

At 4077, a high pressure side concentrate outlet line for reverseosmosis unit B is shown directed to joint 4078, where it combined withliquid in line 4079. The liquid in line 4079 comprises liquid from line4023 pressurized at reverse osmosis pump 4080. The combined stream at4081 comprises a high pressure side concentrate inlet flow line toreverse osmosis unit F. At 4085, a high pressure side concentrate outletflow from reverse osmosis unit F is shown. This liquid is directedthrough pump 4086, and then into high pressure side inlet line 4087 forreverse osmosis unit A. A high pressure side concentrate outlet fromreverse osmosis unit A is shown directed to pressure reduction orstep-down unit 4089, and into line 4002 as concentrate outlet from thesystem 4000.

In general terms, again, system 4000 of FIG. 13 is analogous to system3000, FIG. 12, except for the introduction of reverse osmosis units F, Gand H, one each positioned between two consecutive ones of reverseosmosis units A, B, C and D. Reverse osmosis units F, G and H are usedto balance the concentration of the solution being added to the highpressure side of the system at the joints 4078, 4069, and 4061, with theconcentration of the solution being bypassed from the low pressure sideto the high pressure side of the system via pumps 4080, 4071 and 4062.This renders a more efficient system, with respect to overall use ofenergy, because a concentrated solution would not be diluted as wouldotherwise be the case in system 3000 (FIG. 12) at joints 3076, 3068 and3061.

It is also noted that each of units A, B, C, D, F, G and H is operatedwith: a high pressure side (concentrate) inlet; a high pressure side(concentrate) outlet; a low pressure side inlet; and, a low pressureside (solvent) outlet. The final reverse osmosis unit E is not conductedwith a low pressure side inlet, and comprises a final solvent-generatingreverse osmosis unit.

It is noted that the principles described with respect to system 4000,FIG. 13 can be applied in a variety of alternate configurations, withalternate numbers of reverse osmosis units.

Indeed, it is noted that the principles of the systems of FIGS. 11-13can be practiced with an alternate number of units and with solutionflow entering or exiting the system at differing locations in thesystem. Further, some variations in pump locations and line directioncan be accommodated without substantially varying from the principles.With respect to units F, G and H, FIG. 13, it is noted that one wouldexpect that each of these could be a smaller or shorter reverse osmosismembrane unit in terms of membrane surface area (relative to unit A, B,C and D) as less permeate would generally need to be pushed from thehigher pressure side of the system to the lower pressure side of thesystem through the reverse osmosis membrane of each of the units F, Gand H.

V. Some General Comments and Observations A. Principles and TechniquesRelating to Reverse Osmosis Unit 26, FIG. 2A

Herein, as shown in FIG. 2A, a reverse osmosis unit is provided. Thereverse osmosis unit includes: a reverse osmosis membrane arrangement; ahigh pressure side feed inlet; a low pressure side feed inlet; a highpressure side outlet; and, a low pressure side outlet. During operationof the reverse osmosis unit, the high pressure side outlet operates as aconcentrate outlet relative to the system inlet feed 32; and, the lowpressure side outlet provides for the outlet flow of dilute solution(purified solvent) relative to the system inlet feed 32, from the unit.

In selected example systems according the present disclosure, a reverseosmosis unit is configured for counter current flow with respect to ahigh pressure side flow and the low pressure side flow, duringoperation. In general terms, this references the fact the high pressureside inlet and the low pressure side inlet are at or near opposite endsof the reverse osmosis unit; and, the high pressure side outlet and thelow pressure side outlet are at or near opposite ends of the reverseosmosis unit, although alternatives are possible.

Herein, reverse osmosis systems including at least one reverse osmosisunit in accord with the reverse osmosis characterization above, areprovided. In a number of systems characterized herein, the reverseosmosis system includes at least two reverse osmosis units, each of thetwo including: a reverse osmosis membrane arrangement; a high pressureside feed inlet; a low pressure side feed inlet; a high pressure sideoutlet; and, a low pressure side outlet.

With respect to use of the reverse osmosis unit and system characterizedabove, a process or method for processing a solution is characterizedherein. It is noted that the solution can comprise an original solutionas characterized herein, although the solution being processed cancomprise solution from another step (unit) of the process.

In a typical application, the process involves providing a reverseosmosis unit having: a reverse osmosis membrane arrangement; a highpressure side feed inlet; a low pressure side feed inlet; a highpressure side outlet; and, a low pressure side outlet.

The process further includes directing solution to be processed into thehigh pressure side inlet while also directing a solution (in someinstances, the original solution to be processed and in other instancesan alternate solution) into the low pressure side inlet, and conductinga reverse osmosis process across the reverse osmosis membranearrangement between a high pressure side inlet feed stream and the lowpressure side inlet feed stream.

Typically, the process is conducted under circumstances in which, for aselected reverse osmosis unit, the high pressure side pressure sideinlet feed (stream) and the low pressure side inlet feed (stream)differ, if at all, in solute concentration by no more than 20%, usuallyno more than 15%, and in many instances by no more than 10%. Someexamples are described herein, in which the high pressure side inletfeed (stream) and the low pressure side inlet feed (stream) have thesame solute concentration.

B. Selected Additional Principles and Techniques Relating to, and Commonto, Certain of the Example Systems

According to certain aspects of the present disclosure, a process for,and equipment configured for, processing an original liquid/solutemixture into two process streams is provided. The two process streamsgenerally comprise a system solvent or dilute solution outlet flow and asystem concentrate solution outlet flow. The process generally comprisesof a step of providing a (cascading) reverse osmosis system including atleast:

-   -   (i) a first, final, solvent or dilute solution outlet-generating        reverse osmosis membrane unit;    -   (ii) a first, final, concentrate outlet-generating reverse        osmosis unit; and,    -   (iii) an intermediate reverse osmosis membrane unit system        comprising at lease one reverse osmosis unit.

In general, the process can include configuring the (cascading) reverseosmosis system for the following operation. That is, the processincludes operating the reverse osmosis system to process the solutionsuch that:

(a) Concentrate from the first, final, solvent or dilute solutionoutlet-generating reverse osmosis unit is directed into the intermediatereverse osmosis membrane unit system, as at least part of a feed streamthereto;

(b) Low pressure side outlet (dilute solution) flow from theintermediate reverse osmosis membrane unit system is directed into thefirst, final, solvent or dilute solution outlet-generating reverseosmosis unit as at least part of an inlet feed stream thereto;

(c) Concentrate from the intermediate reverse osmosis membrane unitsystem is directed into the first, final, concentrate outlet-generatingreverse osmosis unit as at least part of an inlet feed stream thereto;and,

(d) Each reverse osmosis unit in the intermediate reverse osmosismembrane unit system is conducted with both a high pressure side inletfeed and a low pressure side inlet feed.

In general terms, each reverse osmosis unit that is operated with both ahigh pressure side inlet feed and a low pressure side inlet feed, isoperated with a concentrate difference between the solutionconcentration on the high pressure and low pressure side of the membrane(concentration of solute) to the maximum extent reasonably allowable,for pressure available and structural integrity of the reverse osmosisunit.

In systems and processes in accord with the general techniques herein,each reverse osmosis unit in the intermediate reverse osmosis membraneunit system is typically operated with a solute concentration directedinto the high pressure side inlet feed thereto within 20% of soluteconcentration, (typically within 15% and usually within 10%), of asolute concentration at a low pressure inlet feed thereto. In someinstances the inlet feed to the high pressure side and to the lowpressure of a selected reverse osmosis unit in the intermediate reverseosmosis membrane unit system, are the same, with respect toconcentration of solute.

Further, each reverse osmosis unit in the intermediate reverse osmosismembrane unit system provides a high pressure side concentrate solutionoutlet flow and low pressure side dilute solution outlet flow; and, theoriginal solution to be processed is directed into at least a selectedone (or more) of the: first, final, solvent or dilute solutionoutlet-generating reverse osmosis membrane unit; the intermediatereverse osmosis membrane unit system; and, the first, final, concentrateoutlet-generating reverse osmosis unit.

C. Further Characterizations of Selected Techniques, Processes andArrangements with Respect to Certain Example Systems

In the arrangements of each of FIGS. 3, 5 and 6, each of which is inaccord with the characterizations in section B above, the arrangement isconfigured for a processes to be conducted in a manner such that theintermediate reverse osmosis membrane unit system comprises at leastthree (3) reverse osmosis units organized having: a most permeateflow-direction reverse osmosis unit; a most concentrate flow-directionreverse osmosis unit; and, at least one central unit.

Further, in the arrangements and processes of FIGS. 3, 5 and 6, theequipment is configured for a step of operating that includes:

(a) Directing the original solution to be processed into both the highpressure and the low pressure side of a selected central unit;

(b) Directing concentrate from the selected central unit ultimately intothe most concentrate flow-direction reverse osmosis unit of theintermediate reverse osmosis membrane unit system;

(c) Directing concentrate from the most concentrate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane unitsystem into the first, final, concentrate outlet-generating reverseosmosis unit;

(d) Directing low pressure side dilute solution outlet flow from theselected central unit ultimately into the most permeate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane unitsystem; and,

(e) Directing low pressure side dilute solution outlet flow from themost permeate flow-direction reverse osmosis unit of the intermediatereverse osmosis membrane unit system into the first, final, solvent ordilute solution outlet-generating reverse osmosis unit.

Further, in the systems of, and practices according to, the arrangementof FIGS. 3, 5 and 6, a process in accord with above characterizations inthis section is facilitated wherein the step of operating includes:

(a) Directing a low pressure side outlet flow (dilute solution) from thefirst, final, concentrate outlet-generating reverse osmosis unit intothe most concentrate flow-direction reverse osmosis unit of theintermediate reverse osmosis membrane unit system;

(b) Directing low pressure side outlet flow (dilute solution) from themost concentrate flow-direction reverse osmosis unit of the intermediatereverse osmosis membrane system ultimately into the most permeateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane system;

(c) Directing low pressure side outlet flow (dilute solution) from themost permeate flow-direction reverse osmosis unit of the intermediatereverse osmosis system into the first, final, solvent or dilute solutionoutlet-generating reverse osmosis membrane unit;

(d) Directing a high pressure side outlet flow (concentrate orconcentrate solution) from the first, final, solvent or dilute solutionoutlet-generating reverse osmosis unit into the most permeateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system;

(e) Directing concentrate from the most permeate flow-direction reverseosmosis unit of the intermediate reverse osmosis unit membrane systemultimately into the most concentrate flow-direction reverse osmosis unitof the intermediate reverse osmosis membrane unit system; and,

(f) directing concentrate from the most concentrate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane unitsystem the first, final, concentrate outlet-generating reverse osmosisunit.

In accordance with the processes characterized as above, conducted forexample, in the example systems of FIGS. 3, 5 and 6, the process andarrangement can be configured such that:

(a) The intermediate reverse osmosis membrane unit system comprisesmultiple reverse osmosis membrane units; and,

(b) the process comprises operating the intermediate reverse osmosismembrane unit system in complete series flow with respect to lowpressure side outlet flow from the first, final, concentrateoutlet-generating reverse osmosis unit to the first, final, solvent ordilute solution outlet-generating reverse osmosis unit. By the term“complete series flow” in this context, it is meant that the flow isdirected through each unit of the reverse osmosis membrane unit system,in series.

(c) Further, the original solution can be directed into one of thereverse osmosis units of the intermediate reverse osmosis membranesystem.

D. Certain Selected Features and Processes in Accord with the Systems ofFIGS. 3 and 5

In the specific example systems and processes characterized above, inconnection with FIGS. 3 and 5, a process in accord with the previouscharacterizations is provided in a manner involving operating theintermediate reverse osmosis membrane unit system specifically with five(5) reverse osmosis units:

(a) in complete concentrate (concentrate solution) flow series from themost permeate flow-direction unit of the intermediate reverse osmosismembrane unit system to the most concentrate flow-direction unit of theintermediate reverse osmosis membrane unit system; and,

(b) in complete dilute solution flow series from the most concentrateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system to the most permeate flow-direction reverse osmosisunit of the intermediate reverse osmosis membrane unit system.

Further, in the arrangements and processes exemplified in FIGS. 3 and 5,the system is configured for conducting the process by operating themost concentrate flow-direction reverse osmosis unit of the intermediatereverse osmosis membrane system with:

(a) a high pressure side inlet flow comprising a combination of:

-   -   (i) concentrate outlet flow from a first next permeate        flow-direction reverse osmosis unit relative to the most        concentrate flow-direction reverse osmosis unit of the        intermediate reverse osmosis membrane unit system; and,    -   (ii) low pressure side dilute solution outlet flow from the        first, final, concentrate outlet-generating reverse osmosis        unit; and,

(b) a low pressure side inlet flow comprising low pressure side dilutesolution outlet flow from the first, final, concentrateoutlet-generating reverse osmosis unit.

In an example process, the high pressure side inlet flow concentrationand the low pressure inlet flow concentration, for the most concentrateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane system, is conducted with streams consisting essentially of theflow concentrations identified.

Further, the step of operating the process, in the system in accord withFIGS. 3 and 5, is operated with the first next permeate flow-directionreverse osmosis unit, relative to the most concentrate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane unitsystem, with:

(a) a high pressure side inlet flow comprising a combination of:

-   -   (i) concentrate flow from a second next permeate flow-direction        reverse osmosis unit from the most concentrate flow-direction        reverse osmosis unit of the intermediate osmosis membrane        system; and,    -   (ii) low pressure side dilute solution outlet flow from the most        concentrate flow-direction reverse osmosis unit of the        intermediate reverse osmosis membrane unit system; and,

(b) a low pressure side inlet flow comprising low pressure side dilutesolution outlet flow from the most concentrate flow-direction reverseosmosis unit of the intermediate reverse osmosis membrane system.

For the particular processes and systems of FIGS. 3 and 5, the highpressure side inlet flow and the low pressure side inlet flow consistessentially of the flows characterized.

Further, the systems of FIGS. 3 and 5 are configured for operation inaccord with the principles herein, including a step of operating thesecond next permeate flow-direction reverse osmosis membrane unitrelative to the most concentrate flow-direction reverse osmosis unit ofthe intermediate reverse osmosis membrane unit system, with:

(a) a high pressure side inlet flow comprising a combination of:

-   -   (i) original solution to be processed;    -   (ii) low pressure side dilute solution outlet flow from the        first next permeate flow-direction reverse osmosis unit relative        to the most concentrate flow-direction reverse osmosis unit of        the intermediate reverse osmosis unit system; and,    -   (iii) concentrate from a third next permeate flow-direction        reverse osmosis membrane unit relative to the most concentrate        flow-direction reverse osmosis unit of the intermediate reverse        osmosis membrane unit system; and,

(b) a low pressure side inlet flow comprising a combination of:

-   -   (i) original solution to be processed; and,    -   (ii) low pressure side outlet flow relative to the first next        permeate flow-direction reverse osmosis unit, relative to the        most concentrate flow-direction reverse osmosis unit of the        intermediate reverse osmosis membrane unit system.

Typically the high pressure side inlet flow and the low pressure sideinlet flow for the second next permeate flow-direction reverse osmosismembrane unit relative to the most concentrate flow-direction reverseosmosis unit of the intermediate reverse osmosis membrane unit systemconsist essentially of the flows characterized.

Still further, a system in accord with either FIGS. 3 and 5 cangenerally be characterized as including features for an operationinvolving operating the third next permeate flow-direction reverseosmosis unit, relative to the most concentrate flow-direction reverseosmosis unit in the intermediate reverse osmosis membrane unit system,with:

(a) a high pressure side inlet flow comprising a combination of:

-   -   (i) low pressure side dilute solution outlet flow from a low        pressure side of the second next permeate flow-direction reverse        osmosis unit, relative to the most concentrate flow-direction        unit of the intermediate reverse osmosis membrane unit system;        and,    -   (ii) concentrate outlet flow from a high pressure side of the        most permeate flow-direction reverse osmosis unit of the        intermediate reverse osmosis membrane unit system; and,

(b) a low pressure side inlet flow comprising:

-   -   (i) low pressure side dilute solution outlet flow from a low        pressure side of the second next permeate flow-direction reverse        osmosis unit, relative to the most concentrate downstream unit        of the intermediate reverse osmosis membrane unit system.

Typically the high pressure side inlet flow concentration and the lowpressure side inlet flow, of the third next permeate flow-directionreverse osmosis membrane unit, relative to the most concentrateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system, consist essentially of the flows identified.

Further, the systems characterized in either of FIGS. 3 and 5 andoperation of them, can be characterized as being configured foroperating the most permeate flow-direction reverse osmosis unit of theintermediate reverse osmosis membrane unit system, with:

(a) a high pressure side inlet flow comprising a combination of:

-   -   (i) low pressure side dilute solution outlet flow from the third        next permeate flow-direction reverse osmosis unit, relative to        the most concentrate flow-direction reverse osmosis unit of the        intermediate reverse osmosis unit system; and,    -   (ii) concentrate outlet from the first, final, solvent        outlet-generating reverse osmosis membrane unit; and,

(b) a low pressure side inlet flow comprised of low pressure side outlet(dilute solution) flow from the third next permeate flow-directionreverse osmosis unit, relative to the most concentrate flow-directionunit of the intermediate reverse osmosis membrane unit system.

In a typical process conducted with the systems of FIGS. 3 and 5, thehigh pressure side inlet flow and low pressure side inlet flow, for themost permeate flow-direction reverse osmosis unit of the intermediatereverse osmosis unit system, consist essentially of the flowsconcentrations characterized.

E. Selected Characteristics of a System for, and Process Conducted inAccord with, FIG. 6

In the system characterized herein in connection with FIG. 6, andoperation of that system, the system is generally configured foroperating the intermediate reverse osmosis membrane system with four (4)reverse osmosis units:

(i) In concentrate flow series from a most permeate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane systemto the most concentrate flow-direction reverse osmosis unit of theintermediate reverse osmosis membrane unit system; and,

(ii) In dilute solution flow series from the most concentrateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system to the most permeate flow-direction reverse osmosisunit of the intermediate reverse osmosis membrane unit system.

Further, the system of FIG. 6 can be characterized as configured for,and to be operated in accord with:

(a) Operating the first, final, concentrate outlet-generating reverseosmosis unit with a high pressure inlet flow and a low pressure sideinlet flow comprising (and typically consisting essentially of) the sameinlet solution, in terms of concentrate solute; and,

(b) Operating the first, final, dilute solution outlet-generatingreverse osmosis membrane unit with a high pressure side inlet feed and alow pressure inlet feed comprising (and typically consisting essentiallyof) the same inlet solution, in terms of concentration solute.

F. Some Specific Configurations and Operational Features CharacterizedHerein in Connection with the System of FIG. 7

Herein, the system of FIG. 7 can be characterized as configured foroperation of a process wherein the intermediate reverse osmosis membraneunit system comprises two (2) reverse osmosis membrane units in the formof:

(a) a most concentrate flow-direction reverse osmosis membrane unit;and,

(b) a most permeate flow-direction reverse osmosis membrane unit.

Further, the system can be characterized as a process that includesoperating the first, final, dilute solution outlet-generating reverseosmosis membrane unit with a high pressure side inlet flow comprisinglow pressure side dilute solution outlet flow from the most permeateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system.

Indeed the process can be characterized as operating the first, final,dilute solution outlet-generating reverse osmosis membrane unit with ahigh pressure side inlet flow consisting essentially of the flowscharacterized.

Further the process can be characterized as operating the most permeateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane system with: both a high pressure side inlet flow and a lowpressure side inlet flow having the same concentration in solute, andeach comprising a combination of:

(a) Concentrate outlet flow from the first, final, dilute solutionoutlet-generating reverse osmosis unit;

(b) Original solution to be processed; and,

(c) Low pressure side dilute solution outlet flow from the mostconcentrate flow-direction reverse osmosis unit of the intermediatereverse osmosis membrane unit system.

This specific process is described herein in connection with FIG. 7 asoperating the most permeate flow-direction reverse osmosis membrane unitin the intermediate reverse osmosis membrane unit system with the highpressure side inlet flow and the low pressure side inlet flow consistingessentially of the flows characterized.

The system of FIG. 7 can also be characterized as configured foroperating the most concentrate flow-direction reverse osmosis unit, ofthe intermediate reverse osmosis membrane unit system, with: both a highpressure side inlet flow and a low pressure inlet flow having the sameconcentration, in terms of solute concentration, and comprising acombination of:

(a) Concentrate outlet flow from the most permeate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane unitsystem; and,

(b) Low pressure side dilute solution outlet flow from the first, final,concentrate outlet-generating reverse osmosis unit.

Further, the step of operating the most concentrate flow-directionreverse osmosis membrane unit of the intermediate reverse osmosismembrane unit system can be characterized as operating both the highpressure side inlet flow and the low pressure side inlet flow with flowsconsisting essentially of the flows characterized.

Further, the system of FIG. 7 can be characterized as configured foroperating the first, final, concentrate outlet-generating reverseosmosis unit with both a high pressure side inlet flow and a lowpressure side inlet flow having the same concentration, in solute,comprising concentrate outlet flow from the most concentrateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system.

The specific example system of FIG. 7 can be characterized as configuredfor operating the first, final, concentrate outlet-generating reverseosmosis membrane unit with both a high pressure side inlet flow and alow pressure side inlet flow consisting essentially of the flowscharacterized.

G. Selected Specific Characterizations of Systems and Processes inAccord with FIG. 8

In addition to the selected characterizations directed to the assemblyand process in FIG. 8 characterized above, the assembly of FIG. 8 can becharacterized as configured for operation of a process wherein theintermediate reverse osmosis membrane unit system comprises two (2)reverse osmosis units comprising a most permeate flow-direction reverseosmosis unit and a most concentrate flow-direction reverse osmosis unit.

The process can be characterized as conducted with a high pressure inletfeed to the first, final, solvent outlet-generating reverse osmosis unitcomprising a combination of:

(a) Original solution; and,

(b) Low pressure side dilute solution outlet flow from the most permeateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system.

Further, the process can be characterized as conducted with a highpressure side inlet feed and a low pressure side inlet feed to the mostpermeate flow-direction reverse osmosis unit of the intermediate reverseosmosis membrane unit system being the same in solute concentration andcomprising a combination of:

(a) Concentrate outflow from the first, final, solvent outlet-generatingreverse osmosis membrane unit; and,

(b) Low pressure side dilute solution outlet flow from the mostconcentrate flow-direction reverse osmosis unit of the intermediatereverse osmosis membrane unit system.

Further, the high pressure side inlet feed and the low pressure sideinlet feed to the most concentrate flow-direction reverse osmosis unit,of the intermediate reverse osmosis membrane unit system, can becharacterized as being the same in solute concentration and comprising,in combination:

(a) Concentrate outlet flow from the most permeate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane unitsystem; and,

(b) Low pressure side dilute solution outlet flow from the first, final,concentrate outflow-generating unit.

Finally, a high pressure side inlet feed and a low pressure side inletfeed to the first, final, concentrate-generating reverse osmosis unitcan be characterized as being the same in solute concentration andcomprising concentrate from the most concentrate flow-direction reverseosmosis unit of the intermediate reverse osmosis membrane unit system.

In typical applications of the principles characterized above inconnection with FIG. 8, the assembly is configured so that the processis conducted with the various flows identified herein above consistingessentially of the flows characterized.

H. Further Specific Characterizations of Equipment and Processes Relatedto the System of FIGS. 9 and 10

Herein above, it was characterized that the reverse osmosis units ofFIG. 8, can be configured with alternate feed lines, for still furtherapplication and processes according to the present disclosure. Thesecharacterizations are exemplified, by the systems of FIGS. 9 and 10.

Referring first to the system of FIG. 9, when operated a process isconducted involving an intermediate reverse osmosis unit systemcomprising two reverse osmosis units comprising a most permeateflow-direction reverse osmosis unit and a most concentrateflow-direction reverse osmosis unit. Further, the process is conductedwith:

(a) a high pressure side inlet feed to the first, final, dilutesolution-outlet generating reverse osmosis unit comprising a combinationof:

-   -   (i) original solution; and,    -   (ii) a low pressure side dilute solution outlet flow from the        most permeate flow-direction reverse osmosis unit of the        intermediate reverse osmosis membrane unit system;

(b) a high pressure side inlet feed to the most permeate flow-directionreverse osmosis unit of the intermediate reverse osmosis membrane systemcomprising a combination of:

-   -   (i) a low pressure side dilute solution outlet flow from the        most concentrate flow-direction reverse osmosis unit of the        intermediate reverse osmosis unit system; and,    -   (ii) a high pressure side concentrate outlet flow from the        first, final, dilute solution outlet-generating reverse osmosis        unit;

(c) a low pressure side inlet feed to the most permeate flow-directionreverse osmosis unit of the intermediate reverse osmosis unit systemcomprising concentrate outlet flow from the first, final, dilutesolution outlet-generating reverse osmosis unit;

(d) a low pressure side inlet feed to the most concentrateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit system comprising concentrate outlet flow from the mostpermeate flow-direction unit of the intermediate reverse osmosismembrane unit system;

(e) a high pressure side inlet feed to the most concentrateflow-direction reverse osmosis unit of the intermediate reverse osmosismembrane unit comprising a combination of:

-   -   (i) a low pressure side dilute solution outlet flow from the        first, final, concentrate-generating reverse osmosis unit; and,    -   (ii) a high pressure side concentrate outlet flow from the most        permeate flow-direction unit of the intermediate reverse osmosis        membrane unit system; and,

(f) a high pressure side inlet feed and low pressure side inlet feed tothe first, final, concentrate-generating reverse osmosis unit being thesame in solute concentrate and each comprising concentrate outlet flowfrom the most concentrate flow-direction unit of the intermediatereverse osmosis membrane unit system.

In the system of FIG. 9, typically each of the flows consistsessentially of the flow characterized above.

In FIG. 10, a process or system is also depicted wherein theintermediate reverse osmosis membrane unit system comprises (2) reverseosmosis units comprising a most permeate flow-direction reverse osmosisunit and a most concentrate flow-direction reverse osmosis unit.

Further, when the system of FIG. 10 is operated, a process is conductedwith:

(a) a high pressure side inlet feed to the first, final, dilute solutionoutlet-generating reverse osmosis unit comprising a combination of:

-   -   (i) original solution; and,    -   (ii) a low pressure side dilute solution outlet flow from the        most permeate flow-direction reverse osmosis unit of the        intermediate reverse osmosis membrane unit system;

(b) a low pressure side inlet feed to the most permeate flow-directionreverse osmosis unit of the intermediate reverse osmosis unit systemcomprising a low pressure side dilute solution outlet flow from the mostconcentrate flow-direction reverse osmosis unit of the intermediatereverse osmosis unit system;

-   -   (iv) a high pressure side inlet feed to the most permeate        flow-direction reverse osmosis unit of the intermediate reverse        osmosis unit system comprising concentrate outlet flow from the        first, final, dilute solution outlet-generating reverse osmosis        unit;    -   (v) a high pressure side inlet feed to the most concentrate        flow-direction reverse osmosis unit of the intermediate reverse        osmosis membrane unit system comprising of concentrate outlet        flow from the most permeate flow-direction unit of the        intermediate reverse osmosis membrane unit system;    -   (vi) a low pressure side inlet feed to the most concentrate        flow-direction reverse osmosis unit of the intermediate reverse        osmosis membrane unit system comprising of low pressure side        dilute solution outlet flow from the first, final,        concentrate-generating reverse osmosis unit; and,    -   (vii) a high pressure side inlet feed and a low pressure side        inlet feed to the first, final, concentrate-generating reverse        osmosis unit being the same in solute concentrate and each        comprising concentrate outlet flow from the most concentrate        flow-direction unit of the intermediate reverse osmosis membrane        unit system.

In a typical application of the techniques described herein inconnection with FIG. 10, each feed consists essentially of the flowcharacterized above.

I. Further Specific Characterizations of Equipment and Processes asRelated to the System of FIG. 4.

In addition to being configured for conduct of process steps ascharacterized herein above with respect to FIG. 4, the system of FIG. 4can be further characterized as configured for a process involvingfeatures and characteristics described in this section.

For example, the assembly of FIG. 4 can be characterized as beingconfigured such that the reverse osmosis system includes two (2) finaloutlet-generating reverse osmosis units, characterized herein as a firstand a second final concentrate outlet-generating reverse osmosis unit,respectfully.

Further, the process of FIG. 4 can be characterized as conducted in asystem that comprises an intermediate reverse osmosis membrane unitsystem that includes four (4) reverse osmosis units including a mostpermeate flow-direction reverse osmosis unit. Further, the intermediatereverse osmosis membrane unit system can be characterized as including afirst unit subsystem and a second unit subsystem.

(a) The first unit subsystem can be characterized comprising one reverseosmosis membrane unit, termed herein as a first subsystem reverseosmosis unit.

(b) The second subsystem can be characterized is including or comprisingtwo second subsystems reverse osmosis units, characterized herein as asecond subsystem reverse osmosis unit and a third subsystem reverseosmosis unit.

The process characterized is conducted with:

(a) concentrate outflow from the first, final, dilute solutionoutlet-generating reverse osmosis unit directed in series:

-   -   (A) to the most permeate flow-direction reverse osmosis unit of        the intermediate unit system;    -   (B) through the first reverse osmosis unit of the first unit        subsystem; and,    -   (C) through the first, final, concentrate outlet-generating        reverse osmosis unit; and,

(b) low pressure side dilute solution outlet flow from the second finalconcentrate outlet-generating reverse osmosis unit directed in series:

-   -   (i) through the first, final, concentrate outlet-generating        reverse osmosis unit;    -   (ii) through the third subsystem osmosis unit of the second unit        subsystem;    -   (iii) through the first subsystem reverse osmosis unit of the        first unit subsystem;    -   (iv) through the second subsystem reverse osmosis unit of the        second unit subsystem;    -   (v) through the most permeate flow-direction reverse osmosis        unit of the intermediate reverse osmosis membrane unit system;        and,    -   (vi) through the first, final, dilute solution outlet-generating        reverse osmosis unit.

Further, the system of FIG. 4 can be characterized as having an originalsolution feed being directed into the first subsystem reverse osmosisunit, of the first subsystem.

In addition, the process of FIG. 4 can be characterized as including aninlet flow feed to each of the reverse osmosis units of the intermediatereverse osmosis membrane unit system, which is the same for eachselected unit, in solute concentration. By this it is not meant the samefeed is directed to every unit, but rather to each selected unit a highpressure side inlet feed and the low pressure side inlet feed is thesame, in solute concentration.

Further, a characterization of the assembly of FIG. 4 is that it isconfigured for conduct of a process wherein:

(a) inlet flow feed to the most permeate flow-direction reverse osmosisunit of the intermediate reverse osmosis membrane unit system comprisesa combination of:

-   -   (i) concentrate outlet flow from the first, final, dilute        solution outlet-generating reverse osmosis unit; and,    -   (ii) low pressure side dilute solution outlet flow from the        second subsystem reverse osmosis unit, of the second unit        subsystem;

(b) inlet flow to the second subsystem reverse osmosis unit of thesecond subsystem comprises a low pressure side dilute solution outletflow from the first subsystem reverse osmosis unit of the firstsubsystem;

(c) inlet to the first subsystem reverse osmosis unit of the first unitsubsystem comprises a combination of:

-   -   (i) original solution;    -   (ii) concentrate outflow from the most permeate flow-direction        reverse osmosis unit of the intermediate reverse osmosis        membrane unit system; and,    -   (iii) low pressure side dilute solution outlet flow from the        third subsystem reverse osmosis unit of the second unit        subsystem;

(d) the third subsystem reverse osmosis unit of the second subsystem isoperated with flow comprising a combination of:

-   -   (i) concentrate outflow from the second subsystem reverse        osmosis unit of the second unit subsystem; and,    -   (ii) low pressure side dilute solution outlet flow from the        second final concentrate-generating reverse osmosis unit; and,

(e) the second, final, concentrate-generating reverse osmosis unit beingoperated with flow comprising low pressure side outlet flow from thefirst, final, concentrate-generating reverse osmosis unit; and,

-   -   (ii) concentrate outflow from the first reverse osmosis unit of        the first subsystem.

In a typical process in accord with the system of FIG. 4, flows consistessentially of flows characterized, and, again, the same flow, for eachselected unit, is provided to the high pressure side and low pressureside.

J. Further Specific Characterizations of Equipment and ProcessesRelating to the System of FIG. 9A.

According to FIG. 9A, a process of conducting of reverse osmosisprocessing of an original stream is provided which includes a step ofproviding reverse osmosis unit system including at least: a firstreverse osmosis unit having a reverse osmosis membrane arrangement, ahigh pressure side inlet feed, a low pressure side feed inlet, a highpressure side outlet and a low pressure side outlet; a second reverseosmosis unit having reverse osmosis membrane arrangement, a highpressure side feed inlet, a low pressure side feed inlet, a highpressure side outlet and a low pressure outlet; and, a third reverseosmosis unit having a reverse osmosis membrane arrangement, a highpressure side feed inlet, a high pressure side outlet and a low pressureside outlet. Of course the third reverse osmosis unit can also include alow pressure side feed inlet and the system can include still furtherunits.

The process generally involves the reverse osmosis system with:

-   -   (i) original solution feed into the high pressure side feed        inlet of the first reverse osmosis unit;    -   (ii) low pressure outlet flow from the first reverse osmosis        directed into the second reverse osmosis unit of the high        pressure side inlet feed;    -   (iii) high pressure side outlet flow from the second reverse        osmosis unit directed into low pressure side inlet feed of the        first reverse osmosis unit;    -   (iv) a low pressure side outlet from the second reverse osmosis        unit directed into the high pressure side inlet of the third        reverse osmosis unit;    -   (v) no original solution feed into the low pressure side of the        first reverse osmosis unit; and,    -   (vi) no low pressure side outlet flow from the first reverse        osmosis unit directed into the low pressure side inlet feed to        the second reverse osmosis unit.

Conducting the process in the manner characterized above, provides forisolation of a flow loop involving the low pressure side of the firstreverse osmosis unit and a high pressure side of the second reverseosmosis unit, to advantage. For example, the high pressure side inletfeed to the high pressure side inlet of the second reverse osmosis unitcan be different in solute, from a low pressure side inlet feed to thesecond reverse osmosis unit. By “different solute” in this context, itis meant that a component of the solute in the high pressure side can bedifferent from a component of the solute in the low pressure side. Forexample, a component can be present on the high pressure side which isabsent on the low pressure side, or present in the low pressure sidewhich is absent from the high pressure side, or overall solutecomposition can be different between the two with respect to compositionand relative composition, not merely concentration. Also, high pressureside inlet feed to the high pressure side inlet of the second reverseosmosis unit can be different in at least one of solute and solvent froma low pressure side inlet feed to the second reverse osmosis unit.However, it should be noted that if initiated and used with differentsolvents, at some point in the process a solvent will tend to migrateacross the membrane from the high pressure side toward the low pressureside.

Similar techniques can be used for other isolating of loops within thereverse osmosis unit system.

K. Further Specific Characterizations of Equipment and ProcessesRelating to the Systems of FIGS. 11-13

According to FIGS. 11-13, a process of conducting a reverse osmosisprocessing of an original stream is provided which include steps inwhich: the intermediate reverse osmosis membrane unit system is operatedwith multiple reverse osmosis membrane units; and, the intermediatereverse osmosis membrane unit system is operated with no pressurereduction, or pressure step-down step, conducted in liquid flow pathsbetween any of the reverse osmosis membrane units in the intermediatereverse osmosis membrane unit system. This can lead to energy savingsadvantage as characterized above.

With respect to the specific example system of FIG. 12, the system isconfigured for, and the process is conducted with, a low pressure sideoutlet flow from at least one reverse osmosis membrane unit in theintermediate reverse osmosis membrane unit system being split into twostreams: (a) a first stream which is directed into a low pressure sideinlet stream of a next permeate flow direction reverse osmosis membraneunit; and, (b) a second stream which is pressurized and is then directedinto a high pressure side outlet stream for the next upstream,concentrate flow direction, reverse osmosis unit. Indeed, a process isshown in FIG. 12 which these steps are conducted for more than onereverse osmosis membrane unit in the intermediate reverse osmosismembrane unit system.

In the variation of FIG. 13, the system is configured for, and theprocess is conducted with, a low pressure side outlet flow from at leastone reverse osmosis membrane unit in the intermediate reverse osmosismembrane unit system being split into two streams: (a) first streamwhich is directed into a low pressure side inlet stream of the nextpermeate direction reverse osmosis membrane unit; and, (b) a secondstream which is pressurized and is then directed into a high pressureside inlet stream for the next upstream concentrate flow-directionreverse osmosis membrane. Indeed, the process is shown in FIG. 13 inwhich these steps are conducted for more than one reverse osmosismembrane unit in the intermediate reverse osmosis system.

L. Further Comments

It is noted that a variety of systems and processes are characterizedherein, for conduct of a cascading reverse osmosis process. Thetechniques can be applied in a variety of alternate processing equipmentconfigurations, while obtaining advantage of the characterizationsprovided herein.

It is noted that a variety of specific equipment locations andconfigurations (pump locations, pressure reducer locations and linedirections) are indicated in the figures. Alternate locations andconfigurations, for some applications, are feasible, while maintaining apractice of general processing techniques according to the presentdisclosure.

In the next section, a hypothetical example is provided, indicating anexample of the utility of the principles according to the presentdisclosure.

VII. A Hypothetical Example (Using the System of FIG. 7)

This engineered example is provided to illustrate one of the manypotential uses of the invention and to illustrate the advantages of thismethod compared to the existing conventional, prior art, methods. Theexample is based on the system of FIG. 7.

For this example assume a fruit juice is being processed to a highconcentration suitable for the frozen concentrate market; and assume theincoming juice stream has a starting fructose sugar concentration of17.36% by weight. 17.36% sugar by weight corresponds to a specificgravity of approximately 1.0505 and is a typical sugar concentrationlevel for fresh pressed apple, or other juices.

For the example assume the juice will be processed at a fixedtemperature of 68° F. through all stages in the process and the pressuredrop in various the conduits carrying solution will be negligible.

For the example it has been assumed that each reverse osmosis (RO) unitwill have a solution flow related pressure drop of 15 feet of watercolumn on both the high pressure and low pressure sides of the membrane.It is also assumed that the efficiency of each pump is 87% and that eachmotor is 92.5% efficient. Each pressure letdown device is assumed to bea turbine style power regenerative device which will be used to assistin the pressurization function that is being provided by eachpressurization pump.

Also, it is assumed that the efficiency for each pressure letdown deviceis 77% effectiveness at converting the available pressure differentialand flow rate into usable power. The example also assumes a drivingdifferential pressure across the membrane arrangement in each reverseosmosis (RO) unit at a level which is 40% higher than the difference inosmotic pressures that would be ideally required for the two solutionsexiting the high and low pressure sides of the RO unit. This level ofextra pressure is typical of conventional RO systems as a means ofproviding high permeate flux rates and to also overcome theconcentration gradients which will inherently exist in the solutionsnear the membrane wall. This engineered example is described assuming asteady state, steady flow condition.

The solution (juice) to be processed enters the system 700 via conduit701 at a concentration of 17.36% fructose by weight and is pressurizedby pump 705 from an entering pressure in conduit 701 of zero Pounds perSquare Inch Gage (PSIG) to a pressure of 678 PSIG at a flow rate of1,210 pounds per minute (#/min) of solution in line 706. The solutioncomprises 210 #/min of solute (fructose) and 1000 #/min of solvent(water). The shaft power required at the assumed efficiencies would be66 break horsepower (BHP). The solution is then conducted via conduit706 to where it combines with flows of solution of the sameconcentration (17.36% concentration by weight) leaving reverse osmosis(RO) unit D and reverse osmosis (RO) unit B via conduits 780 and 742,respectively. The flow of solution from RO D in conduit 780, afterpressurization at pump 781 contains 270 #/min of solute (fructose) and1287 #/min of solvent (water). The flow of solution from RO B in conduit742 contains 120 #/min of solute (fructose) and 573 #/min of solvent(water).

The combined flow of solution flows at a rate of 3,460 #/min at 17.36%concentration by weight to joint 707 where it splits off into twoseparate streams that carry solutions of equal concentration toward eachside of a common membrane arrangement via conduits 708, 709. Conduit 708conducts 55% of the solution flow to the high pressure side of reverseosmosis (RO) unit A. Conduit 704 conducts 45% of the solution flow topressure letdown device 713 where it is then conducted via conduit 714to the low pressure side of reverse osmosis (RO) unit A. At the assumedefficiencies pressure letdown device 713 would be expected to produce 46BHP and be utilized in assistance of RO pump 771. Because the solution'sconcentration entering RO unit A on the high pressure side 715 x of themembrane 715 is the same as the solution's concentration on the lowpressure side 715 y of the membrane 715, a flux of permeate/solvent willbe established through the membrane 715 causing the solutionconcentration to rise in solute per unit of solvent on the high pressureside 715 x of the membrane 715 as it travels through reverse osmosis(RO) unit A, while at the same time causing a fall in solutionconcentration (or a solution dilution with permeate/solvent) as ittravels through the low pressure side 715 y of reverse osmosis (RO) unitA. According to this engineered example the pressure on the high side715 x of reverse osmosis (RO) unit A will be 678 PSIG and the pressureon the low pressure side of 715 y reverse osmosis(RO) unit A will bereduced, via pressure dropping device 713 to 133 PSIG. This results in anet differential pressure across the membrane 715 of 545 PSIG. Thecalculated permeate through the membrane 715 at the assumptions outlinedin this engineered example is 704 #/min of solvent (water). Thispermeate is thus combined with the solution traveling through the lowpressure side 715 y of reverse osmosis (RO) unit A and exits unit A viaconduit 770.

The solution exiting unit A via conduit 770 is now 11.94% fructose byweight and has a calculated osmotic pressure of 247 PSIG. The solutionexiting unit A via conduit 720 is now 27.6% fructose by weight and has acalculated osmotic pressure of 636 PSIG. By conservation of mass flow,the solutions entering and exiting on either side the membrane 715contain the same amount of fructose flow since only permeate is allowedto permeate through the membrane. The solution on the low pressure side715 y of the membrane 715 is thereby getting diluted as its total massflow increases with the addition of the permeate through the membrane715, while the solution on the high pressure side 715 x is beingconcentrated as the total mass flow on that side of the membrane isdecreasing as a result of the lost permeate/solvent through the membraneto the low pressure side 715 y. The flow of solution exiting unit A viaconduit 770 contains 270 #/min of solute and 1991 #/min of solvent. Theflow solution exiting unit A via conduit 720 contains 330 #/min ofsolute and 869 #/min of solvent.

The solution of increased concentration leaving the high pressure side715 x of unit A is then conducted via conduit 720 towards unit B andcontinues as described in the paragraphs for unit B (FIG. 7). Thedecreased concentration solution leaving the low pressure side 715 ofunit A is then conducted via conduit 770 to RO pump 771 as it travelstowards unit D. Pump 771 conveys and pressurizes the solution from apressure of 127 PSIG to a pressure of 520 PSIG requiring 71 shaft BHP.

Solution flows via conduit 773 from pump 771 to the high pressure side775 x of unit D at a concentration of 11.95% fructose by weight at apressure of 520 PSIG. The pressure on the low pressure side of unit Dfor this example is assumed to be zero PSIG. The permeate exiting out ofthe system via conduit 778 is assumed to be pure solvent (water). Theflow rate of permeate through the membrane 775, of unit D, is calculatedbased on a total mass flow balance of the system to be 704 #/min. Atthis rate of permeate at 778 out of the system 700; the concentration ofsolution exiting unit D via conduit 780 would be 17.36% by weight whichmatches the concentration of solution entering the system via conduits701 and 706. In this engineered example the system is balanced such thatthe concentration of solutions mixing together from conduits 742, 706and 780 to form the flow to joint 707 are all of the same concentration.The osmotic pressure of the solution exiting unit D via conduit 780 iscalculated to be 371 PSIG. The pressure on this side of the membrane 775is 520 PSIG (40% more than the calculated osmotic pressure). Thispressure differential causes the desired flux of permeate/solventthrough the membrane in unit D. The flow of solution exiting unit D viaconduit 780 contains 270 #/min of solute and 1,287 #/min of solvent.

The solution of increased concentration leaving the high pressure side775 x of unit D is then conducted conduit 780 to 781 as it travelstowards unit A. Pump 781 conveys and pressurizes the solution from apressure of 513 PSIG in conduit 780 to a pressure of 678 PSIG downstreamof the pump 781, requiring 21 shaft BHP. The solution travels via thedepicted conduit towards unit A and continues as described in theparagraphs above for unit A, (FIG. 7).

The solutions from conduits 720 and 767 are of the same concentration(27.55% concentration by weight) leaving unit A and unit C via conduits720 and 765, respectively. The flow of solution from unit A and unit Cin these conduits is as described in the description of FIG. 7.

The combined flow of solution flows via conduit 725 at a rate of 1,751#/min at 27.55% concentration by weight to where it splits off into twoseparate streams that carry solutions of equal concentration toward eachside of a common membrane 735 via conduits 728, 727. Conduit 727conducts 75% of the solution flow to the high pressure side 735 x ofunit B. Conduit 725 conducts 25% of the solution flow to pressureletdown device 730 where it is then conducted via conduit 731 to the lowpressure side 735 y of unit B. At the assumed efficiencies, pressureletdown device 730 would be expected to produce 15 BHP and be utilizedin assistance of pump 741. Because the solution's concentration enteringunit B on the high pressure side 735 x of the membrane 735 is the sameas the solution's concentration on the low pressure side 735 y of themembrane 735, a flux of permeate/solvent will be established through themembrane 735 causing the solution concentration to rise in solute perunit of solvent on the high pressure side 735 x of the membrane 735 asit travels through unit B, while at the same time causing a fall insolution concentration (or a solution dilution with permeate/solvent) asit travels through the low pressure side 735 y of unit B. According tothis engineered example the pressure on the high side 735 x of unit Bwill be 672 PSIG and the pressure on the low pressure side 735 y of unitB will be reduced, via pressure dropping device 730 to 13 PSIG. Thisresults in a net differential pressure across the membrane 735 of 659PSIG. The calculated permeate through the membrane 735 at theassumptions outlined in this engineered example is 256 #/min of solvent(water). This permeate is thus combined with the solution travelingthrough the low pressure side 735 y of unit B and exits unit B viaconduit 740. The solution exiting unit B via conduit 740 is now 17.36%fructose by weight and has a calculated osmotic pressure of 371 PSIG.The solution exiting unit B via conduit 745 is now 34.22% fructose byweight and has a calculated osmotic pressure of 841 PSIG. The flow ofsolution exiting unit B via conduit 740 contains 120 #/min of solute and573 #/min of solvent. The flow solution exiting unit B via conduit 745contains 362 #/min of solute and 696 #/min of solvent.

The solution of increased concentration leaving the high pressure side735 x of unit B is then conducted via conduit 745 towards unit C andcontinues as described below for FIG. 7. The decreased concentrationsolution leaving the low pressure side 735 y of unit B is then conductedvia conduit 740 to pump 741 as it travels towards unit A. Pump 741conveys and pressurizes the solution from a pressure of 7 PSIG inconduit 740 to a pressure of 678 PSIG in conduit 742 requiring 37 shaftBHP.

The solution from unit B flows via conduit 745 at a rate of 1,058 #/minat 34.22% concentration by weight to where it splits off into twoseparate streams that carry solutions of equal concentration toward eachside of a common membrane 755 via conduits 748 and 747. Conduit 747conducts 58% of the solution flow to the high pressure side of unit C.Conduit 748 conducts 42% of the solution flow to pressure letdown device747 where it is then conducted via conduit 750 to the low pressure side755 y of unit C. At the assumed efficiencies, pressure letdown device747 would be expected to produce 16 BHP and be utilized in assistance ofpump 766. Because the solution's concentration entering unit C on thehigh pressure side 755 x of the membrane 755 is the same as thesolution's concentration on the low pressure side 755 y of the membrane755, a flux of permeate/solvent will be established through the membrane755 causing the solution concentration to rise in solute per unit ofsolvent on the high pressure side 755 x of the membrane 755 as ittravels through unit C, while at the same time causing a fall insolution concentration (or a solution dilution with permeate/solvent) asit travels through the low pressure side 755 y of unit C.

According to this engineered example the pressure on the high side 755 xof unit C will be 665 PSIG and the pressure on the low pressure side 755y of unit C will be reduced, via pressure dropping device 747 to 7 PSIG.This results in a net differential pressure across the membrane 755 of658 PSIG. The calculated permeate through the membrane 755 at theassumptions outlined in this engineered example is 108 #/min of solvent(water). This permeate is thus combined with the solution travelingthrough the low pressure side of unit C and exits unit C via conduit765. The solution exiting unit C via conduit 765 is now 27.55% fructoseby weight and has a calculated osmotic pressure of 636 PSIG. Thesolution exiting unit C via conduit 760 is now 41.5% fructose by weightand has a calculated osmotic pressure of 1,107 PSIG. The flow ofsolution exiting unit C via conduit 765 contains 152 #/min of solute and400 #/min of solvent. The flow solution exiting unit C via conduit 760contains 210 #/min of solute and 296 #/min of solvent.

The solution of increased concentration leaving the high pressure side755 x of unit C is then conducted via conduit 760 to pressure letdowndevice 761 where it is then conducted via conduit 702 to the ConcentrateOut exit of the system. At the assumed efficiencies, pressure letdowndevice 761 would be expected to produce 18 BHP and be utilized inassistance of pump 705. The decreased concentration solution leaving thelow pressure side 755 y of unit C is conducted via conduit 765 to pump766 as it travels towards unit B. Pump 760 conveys and pressurizes thesolution from a pressure of 0 PSIG in conduit 765 to a pressure of 672PSIG in conduit 767 requiring 30 shaft BHP.

The results of this engineered indicate a total net power inputrequirement of 225 shaft BHP via reverse osmosis pumps 705, 771, 741,766 and 781, and a total power generated via pressure letdown devices713, 730, 747 and 761 of 95 shaft BHP for a net total system power inputrequirement of 130 shaft BHP. Using the assumed electrical motorefficiencies of 92.5% this equates to a total power input requirement of105 kW (385,260 Btu/hr) to process a 17.36% solution by weightcontaining 210 #/min of solute (fructose) and 1,000 #/min of solvent(water) into two separate streams; one concentrated 702 stream at 41.5%concentration by weight containing 210 #/min of solute (fructose) and296 #/min of solvent (water), and one stream 703 of solvent (water)flowing at a rate of 704 #/min (42,240 #/hour).

The outgoing system 700 concentrated solution is 41.5% fructose byweight. This would have a calculated osmotic pressure of 1,107 PSIG.Using the 40% extra pressure above the osmotic pressure to drive theflux through the membrane to accommodate some level of concentrationgradient near the membrane walls would indicate a pressure required toachieve this final concentration of 1550 PSIG. The maximum workingpressure achievable in presently available reverse osmosis membranes is690 PSIG. Thus achieving this level of concentration through theutilization of the currently available prior art technology would not bepossible without use of the present invention.

To further illustrate the utility of this process a comparison of energyuse was made to that of a conventional prior art systems typically usedin the juice concentrating industry. A single stage evaporator wouldtypically utilize steam or some other heat source to drive anevaporation process whereby water would be evaporated from the juiceleaving behind a concentrated juice product. The energy required for atypical single stage evaporator to evaporate 42,240 #/hour would beapproximately 41,000,000 Btu/hr versus the 385,260 Btu/hr required inthis engineered example, a savings of over 99%. Due to the high energyinput of conventional single effect evaporation many processors utilizedouble, triple, or more effects of evaporation. It is generally acceptedthat a double effect evaporator will utilize approximately half theenergy of a single effect evaporator and a triple effect evaporator willutilize approximately one third the energy of a single effectevaporator, and so on. The energy savings of the present system (FIG. 7)are so dramatic compared to the currently utilized multiple effectevaporation processes that even utilizing a triple effect evaporatorwould consume approximately 13,660,000 Btu/hr compared to the 385,260Btu/hr consumed in this engineered example of the present disclosurewould still represent a savings of approximately 97% in comparison, i.e.the process described above (FIG. 7) would consume only 3% of the energyrequired by the currently utilized prior art.

Similar energy use comparisons were also made against other evaporationprocesses such as Thermal Vapor Recompression (TVR) and Mechanical VaporRecompression (MVR) processes. A typical single stage TVR processesutilizes steam driven thermal compressors and is able to evaporateapproximately 1.5 more water than the steam consumed by the process. Theprocess described above for FIG. 7 represents a 98.7% energy savingsover the typical single stage TVR process. MVR processes can very agreat deal; however, the inventor has knowledge of several MVR processesof similar scale to this engineered example in the fruit pureeconcentrating industry which consume approximately 1 horsepower per 50#/hr of water evaporated. If such an MVR process were to be utilized toevaporate the 42,240 #/hr separated in this engineered example it wouldconsume 844.8 horsepower as compared to the 130 horsepower of thepresent invention, a power consumption savings of 84.6%.

Savings of these magnitudes could be expected to represent a tremendouscompetitive advantage to juice processors and energy saving advantagesfor society as a whole.

What is claimed is:
 1. A process for processing a solution; the processcomprising: with a reverse osmosis system including: (a) a first solventoutlet-generating reverse osmosis unit including: a high pressure sideinlet; a high pressure side outlet; and, a low pressure side outlet;and, (b) an intermediate reverse osmosis unit system including at leasta first intermediate reverse osmosis unit having: a high pressure sideinlet; a low pressure side inlet; a high pressure side outlet; and, alow pressure side outlet; operating the reverse osmosis system suchthat: (i) solution is directed into the high pressure side inlet of thefirst solvent-generating reverse osmosis unit; (ii) solvent is removedfrom the low pressure side outlet of the first solvent-generatingreverse osmosis unit; (iii) there is no low pressure side inlet flowinto the first solvent outlet-generating unit; (iv) outlet flow from thehigh pressure side outlet of the first solvent-generating osmosis unitis directed into the high pressure side inlet of the first intermediatereverse osmosis unit; (v) the first intermediate reverse osmosis unit isoperated with: a high pressure side inlet flow; a low pressure sideinlet flow; a high pressure side outlet flow; and, a low pressure sideoutlet flow (vi) flow into the high pressure side inlet of the firstsolvent outlet-generating reverse osmosis unit comprises the lowpressure side outlet flow from the first intermediate reverse osmosisunit.
 2. A process according to claim 1 wherein: (a) the high pressureside inlet flow to the first intermediate reverse osmosis unit comprisesthe outlet flow from the high pressure side outlet of the firstsolvent-generating reverse osmosis unit and solution that does notcomprise the high pressure side outlet of the first solvent-generatingreverse osmosis unit.
 3. A process according to claim 1 wherein: (a) thehigh pressure side inlet flow to the first intermediate reverse osmosisunit system comprises inlet feed to the reverse osmosis system.
 4. Aprocess according to claim 2 wherein: (a) the solution that does notcomprise the high pressure side outlet of the first solvent-generatingreverse osmosis unit comprises inlet feed to the reverse osmosis system.4. A process according to claim 2 wherein: the reverse osmosis system issuch that: (a) the intermediate reverse osmosis unit system includes atleast a second intermediate reverse osmosis unit having: a high pressureside inlet; a low pressure side inlet; a high pressure side outlet; and,a low pressure side outlet; and, the operating is such that: (i) atleast a portion of high pressure side outlet flow from the firstintermediate reverse osmosis unit is directed into the high pressureside inlet of the second intermediate reverse osmosis unit; and, (ii)the solution that does not comprise the high pressure side outlet of thefirst solvent-generating reverse osmosis unit comprises at least aportion of low pressure side outlet flow from the second intermediatereverse osmosis unit.
 5. A process according to claim 1 wherein: thereverse osmosis system is such that: (a) the intermediate reverseosmosis unit system includes at least a second intermediate reverseosmosis unit having: a high pressure side inlet; a low pressure sideinlet; a high pressure side outlet; and, a low pressure side outlet;and, the operating is such that: (i) at least a portion of high pressureside outlet flow from the first intermediate reverse osmosis unit isdirected into the high pressure side inlet of the second intermediatereverse osmosis unit; and, (ii) at least a portion of low pressure sideoutlet flow from the second intermediate reverse osmosis unit isdirected into the low pressure side inlet of the first intermediatereverse osmosis unit.
 6. A process according to claim 5 wherein: thereverse osmosis system is such that: (a) the intermediate reverseosmosis unit system includes at least a third intermediate reverseosmosis unit having: a high pressure side inlet; a low pressure sideinlet; a high pressure side outlet; and, a low pressure side outlet;and, the operating is such that: (i) at least a portion of high pressureside outlet flow from the second intermediate reverse osmosis unit isdirected into the high pressure side inlet of the third intermediatereverse osmosis unit; and, (ii) at least a portion of low pressure sideoutlet flow from the third intermediate reverse osmosis unit is directedinto the low pressure side inlet of the second intermediate reverseosmosis unit.
 7. A process according to claim 1 wherein: (a) the step ofdirecting solution into the high pressure side inlet of the firstsolvent outlet-generating reverse osmosis unit comprises directingaqueous solution into the high pressure side inlet of the first solventoutlet-generating reverse osmosis unit.
 8. A process according to claim1 wherein: (a) no solution is directed into the first solventoutlet-generating reverse osmosis unit that has not passed through areverse osmosis unit and through a low pressure side outlet of a reverseosmosis unit.
 9. A process according to claim 1 wherein: the reverseosmosis system is such that: (a) the intermediate reverse osmosis unitsystem includes at least a second intermediate reverse osmosis unithaving: a high pressure side inlet; a low pressure side inlet; a highpressure side outlet; and, a low pressure side outlet; and, (b) theintermediate reverse osmosis unit system includes at least aconcentrate-generating reverse osmosis unit having: a high pressure sideinlet; a low pressure side inlet; a high pressure side outlet; and, alow pressure side outlet; and, operating the reverse osmosis unit systemsuch that: (i) at least a portion of high pressure side outlet flow fromthe first intermediate reverse osmosis unit is directed into the highpressure side inlet of the second intermediate reverse osmosis unit;and, (ii) at least a portion of low pressure side outlet flow from thesecond intermediate reverse osmosis unit is directed into the lowpressure side inlet of the first intermediate reverse osmosis unit;(iii) at least a portion of high pressure side outlet flow from thesecond intermediate reverse osmosis unit is directed into the highpressure side inlet of the concentrate-generating reverse osmosis unit;(iv) at least a portion of low pressure side outlet flow from theconcentrate-generating reverse osmosis unit is directed into the lowpressure side inlet of the second intermediate reverse osmosis unit; and(v) at least a portion of high pressure side outlet flow from the secondintermediate reverse osmosis unit is directed into the low pressure sideinlet of the concentrate-generating reverse osmosis unit.
 10. A processaccording to claim 9 wherein: (a) low pressure side outlet flow from theconcentrate-generating reverse osmosis unit is directed into theintermediate reverse-osmosis unit system.
 11. A process according toclaim 1 wherein: the reverse osmosis is such that: (a) the intermediatereverse osmosis unit system includes a second intermediate reverseosmosis unit, which includes: a high pressure side inlet; a highpressure side outlet; a low pressure side inlet; and, a low pressureside outlet; and, (b) the operation is such that the solution receivedfrom the high pressure side outlet of the second intermediate reverseosmosis unit is split into: (i) a first stream; and, (ii) a secondstream.
 12. A process according to claim 11 wherein: (a) the firststream is directed into a low pressure side inlet of a reverse osmosisunit.
 13. A process according to claim 12 wherein: (a) the second streamis directed into a high pressure side inlet of the reverse osmosis unit.14. A process for processing a solution; the process comprising: with areverse osmosis system including: (a) a first solvent outlet-generatingreverse osmosis unit including: a high pressure side inlet; a highpressure side outlet; and, a low pressure side outlet; and, (b) anintermediate reverse osmosis unit system including at least a firstintermediate reverse osmosis unit having: a high pressure side inlet; alow pressure side inlet; a high pressure side outlet; and, a lowpressure side outlet; (c) the intermediate reverse osmosis unit systemincludes at least a second intermediate reverse osmosis unit having: ahigh pressure side inlet; a low pressure side inlet; a high pressureside outlet; and, a low pressure side outlet; and, operating the reverseosmosis unit system such that: (i) solution is directed into the highpressure side inlet of the first solvent-generating reverse osmosisunit; (ii) solvent is removed from the low pressure side outlet of thefirst solvent-generating reverse osmosis unit; (iii) there is no lowpressure side inlet flow into the first solvent outlet-generating unit;(iv) outlet flow from the high pressure side outlet of the firstsolvent-generating osmosis unit is directed into the high pressure sideinlet of the first intermediate reverse osmosis unit; (v) flow into thehigh pressure side inlet of the first solvent outlet-generating reverseosmosis unit comprises low pressure side outlet flow from theintermediate reverse osmosis unit system; (vi) the first intermediatereverse osmosis unit is operated with: a high pressure side inlet flow;a low pressure side inlet flow; a high pressure side outlet flow; and, alow pressure side outlet flow; (vii) the second intermediate reverseosmosis unit is operated with: a high pressure side inlet flow; a lowpressure side inlet flow; a high pressure side outlet flow; and, a lowpressure side outlet flow; (viii) no solution is directed into the firstsolvent outlet-generating reverse osmosis unit that has not passedthrough a reverse osmosis unit and through a low pressure side outlet ofa reverse osmosis unit; (ix) at least a portion of high pressure sideoutlet flow from the first intermediate reverse osmosis unit is directedinto the high pressure side inlet of the second intermediate reverseosmosis unit; (x) at least a portion of low pressure side outlet flowfrom the second intermediate reverse osmosis unit is directed into thelow pressure side inlet of the first intermediate reverse osmosis unit;and (xi) flow into the high pressure side inlet of the first solventoutlet-generating reverse osmosis unit comprises the low pressure sideoutlet flow from the first intermediate reverse osmosis unit.
 15. Aprocess according to claim 14 wherein: (a) the high pressure side inletflow to the first intermediate reverse osmosis unit system comprisesinlet feed to the reverse osmosis system.
 16. A process for processing asolution; the process comprising: with a reverse osmosis systemincluding: (a) a first solvent outlet-generating reverse osmosis unitincluding: a high pressure side inlet; a high pressure side outlet; and,a low pressure side outlet; and, (b) an intermediate reverse osmosisunit system including at least a first intermediate reverse osmosis unithaving: a high pressure side inlet; a low pressure side inlet; a highpressure side outlet; and, a low pressure side outlet; (c) theintermediate reverse osmosis unit system includes at least a secondintermediate reverse osmosis unit having: a high pressure side inlet; alow pressure side inlet; a high pressure side outlet; and, a lowpressure side outlet; and, operating the reverse osmosis unit systemsuch that: (i) solution is directed into the high pressure side inlet ofthe first solvent-generating reverse osmosis unit; (ii) solvent isremoved from the low pressure side outlet of the firstsolvent-generating reverse osmosis unit; (iii) there is no low pressureside inlet flow into the first solvent outlet-generating unit; (iv)outlet flow from the high pressure side outlet of the firstsolvent-generating osmosis unit is directed into the high pressure sideinlet of the first intermediate reverse osmosis unit; (v) flow into thehigh pressure side inlet of the first solvent outlet-generating reverseosmosis unit comprises low pressure side outlet flow from theintermediate reverse osmosis unit system; (vi) the first intermediatereverse osmosis unit is operated with: a high pressure side inlet flow;a low pressure side inlet flow; a high pressure side outlet flow; and, alow pressure side outlet flow; (vii) the second intermediate reverseosmosis unit is operated with: a high pressure side inlet flow; a lowpressure side inlet flow; a high pressure side outlet flow; and, a lowpressure side outlet flow; (viii) no solution is directed into the firstsolvent outlet-generating reverse osmosis unit that has not passedthrough a reverse osmosis unit and through a low pressure side outlet ofa reverse osmosis unit; (ix) at least a portion of high pressure sideoutlet flow from the first intermediate reverse osmosis unit is directedinto the high pressure side inlet of the second intermediate reverseosmosis unit; (x) at least a portion of low pressure side outlet flowfrom the second intermediate reverse osmosis unit is directed into thelow pressure side inlet of the first intermediate reverse osmosis unit;and (xi) the operation is such that solution received from the highpressure side outlet of a selected reverse osmosis unit in theintermediate reverse osmosis unit system is split into: (A) a firststream which is directed into a low pressure side inlet of a reverseosmosis unit; and, (B) a second stream directed into an inlet of areverse osmosis unit.
 17. A process according to claim 16 wherein: (a)the high pressure side inlet flow to the first intermediate reverseosmosis unit system comprises inlet feed to the reverse osmosis system.18. A process according to claim 16 wherein: (a) flow into the highpressure side inlet of the first solvent outlet-generating reverseosmosis unit comprises the low pressure side outlet flow from the firstintermediate reverse osmosis unit.